This is a quick one, well maybe not, and not really technical, just suggestive.
I want to talk about troubleshooting hardware problems with your Computer(PC).

  Say your computer all the sudden just stops working.  Now before I continue, let me say the first thing to do, is determine if you problem is something to do with drivers or software by booting into safe mode.  You can do this by turning on the computer and as soon as you see your screen start to show signs of life, start pressing the F8 key about once a second.  The computer should come up with a screen to select Safe Mode as one of the options.  If you can boot into safe mode then odds are there is a driver or some piece of software that is causing a problem.  Have fun with that
   Mean while back at the ranch, your computer may have not rebooted correctly or just might have crashed while your were doing something or you sat down at it to browse your favorite web page and it was locked up.
  First ask yourself the most important questions of all:
    What have I done lately? 
    Have I installed new software? (not really applicable since were talking about hardware)
    Have I added new hardware?
  If you haven't added/installed anything new or you can't remember doing so, which is my case is most the time.  This is why I have to keep a .txt file on my thumb drive documenting everytime I install or add hardware.  It sucks to start getting old.
  Also ask your self this question, have I done anything like deleting files and I didn't realize what they were, to clean up harddrive space.
  If you answer yes to any of the above questions, it's time to start digging.  First disconnect the new hardware and if possible deinstall the drivers for it.
  After removing/disconnecting the new hardware, reboot the computer and see if you have the same problem.
  First make sure the computer is off, shut it down if possible and if you can't, do it the hard way, turn off the power.  Of course turning off the power should be used as a last resort.  Work you way from the computer to the wall socket.  First try the power button on the front of the computer, if you have one.  Some computers require you to hold the button for 5 to 10 seconds depending on it type.  Some will require you to reach around the back of the computer to flip the switch on the power supply.  That's usually as far as you should have to go.
  I do not recommend using the power strip or unplugging it, do this only if you can't turn it off any other way.
  There are reasons for this, let just say without getting technical that turning a computer off by unplugging the cord from the wall socket or using the power strip is like simulating a power surge and can cause even more damage to the computer.
  Ok, after spouting that out, now that you have the power turned off, unplug ever thing from the computer except for the monitor, keyboard and mouse.  This will eliminate any external device you may have as a possible cause for crashing or causing the computer to lock up.  Once you have done this there should only be a cable plugged into the computer for the Power, keyboard(USB or PS2), mouse(USB or PS2) and the Monitor(DVI or VGA).
  Now try booting the computer and see if it starts up like you would normally expect it to.  If it does, don't start plugging stuff back into it yet.  Give it a day or to and then plug in one item at a time and remember to reboot each time you do.  Hopefully the troublesome device will cause the computer to not boot or crash.  If you find it, get someone that knows how to check the suspected bad device or buy a new one.  Sometimes buying a new one is easier said than done.
  Now the interesting thing here is this doesn't really eliminate all possible hardware, peripherals, devices, or what ever you call them things in the box called a computer.  There are probably still a lot of devices that could cause a problem, hmm, where could they be.   Look inside the box!  You may have a modem, network card(NIC), video card(which is kind of important), scanner interface card(possibly SCSI), etc. etc.  The tough item here most people will not be able to troubleshoot due to the lack of having an extra one laying around the house.  Some geeks like my self, will have to admit, we keep a couple cheap video cards laying around for just such an occasion.   Hell I have to admit, I even have a 17" monitor sitting by my feet right now for just that reason.  Call me crazy
  Anyway, if you can't resolve the problem by disconnecting external devices, it may be possible it's one of your internal devices.  If you don't feel comfortable opening your computer case and removing cards and such, ask someone you may know to help or find you a book for beginners on PC hardware. 

Hope this helps!
Cheers
DougBob