I built my computer about 3 months ago and now it occasionally restarts. I don't know what is causing this but suspect either a bad power supply or CPU or motherboard. How can I determin wich it is or what it is? If it was the power supply wouldn't it just fail to work completely? Any help and opinions would be greatly appreciated. Thanks.

You need to find out what stop error you are getting. By default XP restarts to the desktop after a crash, you can turn this off by... right clicking on 'my computer'....go to properties... then click the 'advanced' tab.... then select.... 'startup and recovery settings'... under 'system failure' ... uncheck 'automatically restart'. Next time your pc crashes note down the stop error and post back results.

memory is also a possible candidate, particularly if you see page fault errors in the event logs try running a few passes with memtest http://hcidesign.com/memtest/download.html

Thank you for your reply's Jeggzy and dannyboy. I am trying both. Will post back results. Thanks.

I'm back with the latest. dannyboy I ran memtest all night and didn't have any errors so it seems the memory is O.K. Jeggzy I did as you suggested and finally got an error message which I will repeat below: A problem has been detected and windows has been shut down to prevent damage to your computer. A wait operation, attach process, or yield was attempted from a DPC routine. If this is the first time you've seen this stop error screen, restart your computer. If this screen appears again, follow these steps: Check to make sure any new hardware or software is properly installed. If this is a new installation, ask your hardware or software manufacturer for any windows updates you might need. If problems continue, disable or remove any newly installed hardware or software. Disable BIOS memory options such as caching or shadowing. If you need to use Safe Mode to remove or disable components, restart your computer, press F8 to select Advanced startup options, and then select Safe Mode. Technical Information: *** STOP 0X000000B8 (0X00000000, 0X00000000, 0X00000000, 0X00000000) Begining dump of physical memory. Physical memory dump complete. Contact your system administrator or technical support group for further assistance. That is exactly what the error message said. Any opinions of what to do next? Seems like a hardware or software comflict? Any help would be appreciated. The only new hardware I installed about 2 months ago was the ATI HDTV Wonder. Could that be causing the conflict?