Troubleshooting computers is like solving the problems you solve in everyday life. Once you understand the basic structure, you can easily determine where the problem lies. Of course, this page is designed to guide you through the steps that are generally taken when a computer fails to operate properly. If you have only one computer and it fails to function properly, this will do you no good (it can't be read on a computer that is inoperative). If you think you may need it later, print it out but before you send it to the printer, do a 'print preview' to be sure that the background is printed white with black text. Printing the background color will use a significant amount of ink/toner.

If your computer fails to power up (you can hear no fans running and no lights are lit when you press the power button), check the following:

• Make sure that you're pressing the power button on the front of the computer and not the reset button.
   
  
• Make sure that the power cord is securely plugged into both the power outlet and the computer's power supply.
   
  
• Make sure that the main power switch on the back of the computer's power supply is on (set to the '1' position). This is shown on page 2 of the tutorial.
   
  
• Make sure that the outlet you have the computer plugged into has power. Unplug the computer and plug a lamp into the same exact socket that the computer is plugged into. If the lamp lights, the outlet has power. If the lamp does not light and it's plugged into an outlet strip, plug the lamp into the wall socket. If the lamp lights when plugged directly into the wall socket but not when plugged into the outlet strip, be sure that the strip's power switch is on. If it has a circuit breaker, be sure that the breaker has not tripped.
   
  
• Make sure that the power switch on the front of the computer is working properly. The power switch should short (connect) the two wires together when you depress the switch. To check this, you'll need a multimeter (set to ohms). You'll place one probe on each wire. If your meter probes can make direct contact with the metal terminal in the plastic connector, do so. If you cannot, you will need to insert two fine, solid wires as is shown in the second photo. The wires are pushed all of the way through to hold them in place and to help ensure that they're making contact with the terminal in the plastic connector housing. You will then touch the probes to the wires to check the switch. Ideally, the ohm meter should read 0 ohms when you depress the switch but many cases use poor quality switches that will not go below ~20 ohms. As long as it goes below ~100 ohms, it's probably OK. You can use a piece of wire (inserted into the back of the plastic connector housing) to short the terminals (to attempt to power up the computer) if you think the switch is at fault. Of course, the connector has to be on the motherboard when you do this. If you are careful and don't short to any other pins, you can short between the two pins for the power switch with anything conductive. If you have a shunt (like the ones used as jumpers on the motherboard or hard drive), you can use that to temporarily (no more than 1 second) short the power switch pins on the motherboard.
   
  
  
  

  Note:
  Many times, the motherboard isn't marked clearly (or at all). The owner's manuals for virtually all motherboards are available for free in PDF format online. Try Googling the model number of the board (generally printed prominently on the board) and 'motherboard manual'. If you haven't yet seen a manual for a motherboard, the one for the board above is HERE. I'd suggest that you only download from the manufacturer's web site if possible. Many of the other 'manuals' sites are infected with malware or force you to jump through hoops to get to the download page. If the download is an exe file, you probably shouldn't download it. It could be infected.

  For times when you can get the computer to power up but need other information about it, try downloading PC Wizard from CPUID.com. PC Wizard can tell you virtually anything you want to know about the computer.

If the lights light up when you press the power button but you get no display, check the following:

• Be sure that the monitor is on.
   
  
• Confirm that you have power to the monitor.
   
  
• If you have an LCD monitor, there may be a small power supply (typically a small rectangular black box) between the wall plug and the plug that connects to the monitor's power supply input. Be sure that the plugs on the power supply and monitor are securely seated.
   
  
• Make sure that the monitor is plugged in securely to the video connector on the back of the computer. This is covered on page 3 of the tutorial. Some monitors have a video cable with removable connectors on both ends so be sure to check the connection on the back of the monitor also.
   
  
• If the monitor still has no display, see if the on-screen display for the monitor's controls can be displayed. You may need to find the owner's manual for your monitor to learn how to access the on-screen display. If the OSD works, the monitor has power but it is possible that the monitor is faulty. If possible, try another monitor on your computer. If another monitor works properly, your monitor may be defective. If another monitor (that's known to be in good working order) doesn't work, you may have problems with your video card or with the video drivers. Try booting to safe mode. If you have video in safe mode, you likely have video driver problems or the video settings are not set to work with your monitor (if the settings are not correct, the monitor will typically alert you to that problem).
   
  
• If the operating system is causing the problem, shut the computer down (hold the power switch on the front of the computer down until the fans stop or disconnect power from the computer). Make sure the monitor is on (power LED will be on but likely amber instead of green). Depress the power switch to start the computer (reconnect power if you had to disconnect it to shut the computer down). After the power switch is pressed, you should hear several fans start and you should see simple (black and white) text on the screen as the computer reboots. If you do, you know the monitor is working. If you don't, the monitor or the monitor cable may be defective. The following is from a computer that didn't have a hard drive in it so it couldn't boot up. A working computer won't show this type of error and will go through this screen so quickly that you won't notice it.

If you've recently installed new graphics card, make sure that the monitor cable is plugged into the new card. Many computers have two or more graphics ports. If it has one on the motherboard's IO panel and a second one in one of the expansion slots, the one in the expansion slot is almost always the one that's going to be used by the computer. If the secondary graphics card is anything other than a basic card, it may need an external power source (from your computer's power supply). Check the installation manual for the graphics card.

Loose Connections:
Many times, a computer will not power up simply because one of the connectors on one of the components inside the computer isn't properly seated. If the computer was moved (or dropped) just prior to it becoming inoperative, there may simply be a loose connection). To check this, unplug the AC mains power plug from the computer's power supply (this is very important). Pull the left side cover off of the computer. On all connectors, gently press them to be sure that they're properly seated. There will likely be be several power supply and IDE connectors that are not to be connected so don't be alarmed if you see connectors that are unplugged. After you've checked all of the connectors, replace the side cover, plug the power cord into the computer's power supply and try to power up the computer.

Improperly Seated Memory Modules:
One very common problem (after a computer has been moved) is improperly seated memory modules. If the computer won't boot up or gives a memory error on the bios screen, shut the computer down, remove and reseat the memory modules. If it still gives an error, you may have to remove all of the modules and install only one at a time (in the various memory slots). If you find that one memory module or one memory slot is causing the error, you will need to avoid using it.

Sometimes, memory problems cause system instability (crashes). If you want to test the memory, download a program like memtest and burn it to a CD. It's a bootable CD so if it's in the CD/DVD drive when you boot the system and the bios setting tell the computer to try to boot to CD first, the memtest software will run automatically. If it makes it through an entire pass, the memory is likely OK.

Power Supply in Protect Mode:
If, when you press the power button, the computer's fans start to turn, then shut off, you could have power supply problems or there may be something loading down the power supply (causing it to go into protective shutdown).

When you press the power switch, the green wire in an ATX power supply is connected to ground (by the motherboard, not directly grounded by the switch). At that point, the power supply is switched on and all of the various voltages are generated. When the various voltages are within a specified tolerance, a signal is generated on another of the power supply pins (the power OK pin) and the processor is then switched on. All of this takes well under a second and most people never realize that it's happening.

ATX power supplies can be tested by disconnecting them from the motherboard and connecting the green wire to any of the black wires. This will turn the supply on. At that point, you can test the individual voltages. If all of them are close to the rated voltage, the supply is likely OK. If the power supply tried to start but wouldn't start (or wouldn't run for more than a second) when it was plugged into the motherboard, you should suspect that something is pulling too much current. Plug the power supply back into the motherboard and disconnect all of the drives' power connectors as well as any accessories such as fans. Again, try to power up the computer. If the PS starts normally, begin reconnecting the power supply to the accessories and drives (one piece at a time and trying to start the machine after each piece is plugged in). If you find that one piece is preventing the machine from starting, you've likely found your problem.

Note:
I've read that some power supplies require a load on one or more of their outputs to power up. I haven't encountered this yet but you should be aware of it.

You may not realize that the actual output voltages are rarely precisely at the rated voltage. The following voltages are from a relatively inexpensive supply. The variation from the rated output that you see here is relatively common and this supply will work fine in most computers. Of course, when the power supply is loaded by the computer, the voltage WILL change somewhat. This is an UN-loaded power supply. As a side note, sometimes the output voltage of some of the outputs will actually increase when the supply is loaded. This often happens when the regulated output (generally the +5 volt output) is loaded down. The reason it happens is that the pulse width of the power supply is increased to maintain the regulated 5 volt output. When the pulse width is increased, all of the other outputs will increase (the 5v output should remain constant). Recently, some power supplies have begun employing two independent sets of regulators. This will help keep more of the output voltages within a tighter tolerance.

If the machine will not start with no accessories plugged in but the power supply powers up fine with the green wire shorted to the black wire (don't try shorting green to black while it's connected to the motherboard), the processor may be dead. This is a somewhat difficult situation. When troubleshooting computers, it's common to simply replace the questionable component with a known good component. Since you won't know whether the motherboard or the CPU is defective, you may want to plug the questionable CPU into a known good test board. If the test board has insufficient protection and the CPU is shorted, the PWM regulator in the test board could be damaged (leaving the board irreparably damaged). If you plug a good CPU into a questionable board that has a defective PWM regulator, then you will kill the test CPU. Many times, if you have a blown CPU, it's best to replace both the CPU and the motherboard. If you decide to swap the CPU to check it, make absolutely sure that you have the correct heatsink properly installed BEFORE applying power to the unit. Some CPUs have no thermal rollback/shutdown protection and if the heatsink isn't properly installed, the CPU will fail within seconds.

When you assemble a new machine or install a major component (motherboard, CPU...), sometimes it won't boot up the first time you turn it on. The problem could be a defective component, a connector that's not properly seated or a BIOS/motherboard setting that isn't right. These are just a few of the possibilities.

• Check the FSB setting. Setting it lower than rated is fine and should allow it to boot if there are no other problems. After you get it booting successfully, you can then set the FSB higher (up to the rated FSB). If the BIOS has an option to select 'failsafe' defaults, that may be a good choice. The computer probably won't run at the absolute fastest possible speed but the settings should ensure that none of the BIOS settings are preventing it from booting.
   
  
• Be sure the memory is properly installed/seated. If you can find no other problems, you could have a defective or incompatible stick of memory. There have been times when a stick of memory wouldn't work in one machine but a different stick (from a different manufacturer) with the same specs would function properly. The stick that wouldn't work in the first machine was fine in other machines. The stick that wouldn't function properly fully passed all memory tests without errors.
   
  
• Be sure you have a working graphics card installed. Generally, the POST (Power On Self Test) beeps will tell you that you have a defective or improperly installed video card. The beeps vary with different bios manufacturers and you should do a Google search for 'POST beeps' to determine what they mean for your bios. For Dell comptuers, they have 4 indicator LEDs to help diagnose problems. You can find the codes by clicking HERE or searching for 'Dell diagnostic code' on Google.
   
  

Sometimes, a computer will simply fail to boot. If you haven't done anything that could be causing problems (installing/updating software/drivers), some of the system files may have become corrupted or some piece of hardware may have failed. If the computer starts to boot (it shows signs of life), it means that the power supply is probably OK. If it repeatedly fails to boot into Windows, you need to try booting to 'safe mode' (covered earlier in the tutorial). If it boots into safe mode, it indicates that the computer's hardware is likely OK and the problem is probably software/driver related. Unless you want to go through extensive troubleshooting, the best thing to do is to go back to the last restore point. Restore Points were covered earlier in the tutorial.

If you installed a new piece of hardware to upgrade an older (but still functional) piece of hardware, the first thing to do is to remove the new piece and reinstall the old component. If the system again begins to boot and works as it did before, the new piece of hardware could be defective or causing some conflict in the system. Its drivers could be corrupt (if you downloaded them) or they may have some sort of incompatibility with your other hardware/software. If you're not going to try to reinstall the new piece of hardware, you should uninstall the drivers for the component that you tried to install.

If the machine will still not boot after reinstalling the old component, you may have pulled a connector out of its socket. Try pushing on all of the connectors on all components (don't forget the memory modules) to be sure that they're all properly seated. If that doesn't work, try booting into safe mode. If it boots there, your hardware is very likely OK and you simply have something loading during boot-up that's causing the system to crash. At this point, you can do a couple of things, you can go back to the last restore point (it should have been created when you installed the drivers for the component that caused the problem). You can boot in safe mode and uninstall the drivers that you recently installed and/or you can go through the startup list (run >> msconfig >> startup) and start removing components until the system boots. If you're removing items from the startup list, begin with the ones that seem to be related to the hardware that you recently installed.

If the computer attempts to boot but crashes repeatedly, boot to safe mode and go to START >> CONTROL PANEL >> ADD AND REMOVE PROGRAMS and uninstall the software. We covered the procedure to uninstall software earlier in the tutorial. If the computer still refuses to boot, you may have to go back to the last restore point.

One of the most important tools for troubleshooting strange software problems is Google. There is no way that any one web site can cover every problem. If you have a problem, take note of the EXACT wording of the problem (take and save a screen-cap if you have a poor memory) and search Google. If you enclose the error statement in parentheses, it may make the search more successful. You may have to follow several links because many of the solutions offered on the forums or in the newsgroups will not be the solution for your problem. If you're having trouble with a specific piece of software, try the software's home page. Look in the 'support' and 'FAQ' sections of the site.

Sometimes, a computer will not boot due to a corrupt file in the OS or a defective hard drive. The problem you face is determining which is the culprit. One tool that you can use is a 'live CD'. A Live CD is a bootable operating system (generally a Linux distribution or a stripped down version of Windows). My favorite is the Hiren Boot CD. It's not always easy to find but if you can find a copy that has mini Windows XP on it, that's the one that I'd suggest that you use, especially if you're working on a computer that was using a Windows operating system. With the live CD, you can go in and confirm that the drive is accessible and the files are generally intact. If, for some reason, the operating system is damaged, you can use the live CD to move the files to a different drive (either a USB flash drive or a second hard drive). If you're going to have to reload the operating system from the Windows installation disc, it's best to make a copy of all important files that are on the same partition as the operating system (generally the partition normally labeled C drive). Sometimes these files will be lost when reloading Windows. If you're going to restore the partition from a recovery file like those produced by True Image or Ghost, EVERY file in the restored partition will be wiped out.

If you can't find a good live CD, you can remove the drive and connect it to another computer. I generally keep a working but generally unused computer around for this. Although it's unlikely, it's possible for malware to infect the computer when the drive is connected to the system. When you do this, you should boot the computer and then connect the drive. If it's a SATA drive it may automatically be recognized. If it's an IDE drive, you will have to go to START >> RIGHT-CLICK MY COMPUTER >> select PROPERTIES >> select the HARDWARE tab >> select DEVICE MANAGER >> RIGHT-CLICK DISK DRIVES >> select SCAN FOR HARDWARE CHANGES. You should see the new drive appear in the list of disk drives. When you go back to Windows Explorer (My Computer), the drive should show up in the list of drives. From there, move the files you need to save.

If the owner of the computer has a lot of important files and can't remember where they all are, the best option may be to simply buy a new hard drive (~$39+ shipping) and load the OS onto the new drive. Then, the owner can move the files to the new drive as they find them. If you do this, make two partitions on the new drive. Make one for the OS. 40-50GB should be plenty. That will leave at least 25GB for the owner to store her files on. It's best (in my opinion) that you not store important files on the OS partition. If you're read the Backing Up Your Hard Drive page, you know that it's also important to have additional backups of important files.

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