A simple hardware troubleshooting step when your computer is locking up or spontaneously restarting, especially during the boot process, is to reseat the expansion cards in your computer.
Reseating, which is just another way of saying "remove-and-reinsert," assures that the card is making a good, clean connection with motherboard. Expansion cards can work loose and get dirty over time so the simple act of removing and reinserting them in their slots on the motherboard will often clear up what might have looked like a major issue.
Reseating the expansion cards in your PC is pretty easy, even if you've never been inside your computer before. It's certainly worth a try before buying new hardware or hauling your computer in for service.
Have you ever fixed a problem by reseating?

Yes, on two occasions. Once when I reseated my Seagate Barracuda 40(!)GB hard drive and completely solved an issue. The other may have been reseating my M – Audio ‘Audiophile’ 24/96 Soundcard, to the same effect.
I’ts definitely worth trying – changing USB cables, firwire even mains cables can sometimes solve issues!
I just wanted to thank you for the reseating idea, because I spent 6 hours troubleshooting and reapplying drivers on my computer in safe mode because of a blue screen from my video card. I never even thought of taking it out until I saw your post. TYVM =)
No problem Nate! Glad I could help. I’m constantly amazed by how often this simple little trick works.
This was a BIG issue back in the days of Windows 95/98. After installing an a modem or any other card, you had only ONE single shot at getting the right drivers recognized by “Plug & Pray”. If your device was not working afterwards, the only way to make “Plug & Pray” recognize it again was to remove it, reboot, remove the drivers ans start anew. I did not know that is an issue today, other than with RAM and Video Cards. THANK YOU – I learned something.
@Robert: No problem. It’s more about shorting and dirty contacts and even gravity working its magic over time than about Windows.