Hopefully this will help others in some way....
Two days ago my computer rebooted (shut down and restarted by itself) while running GPL (Grand Prix Legends). This happened over and over for two solid days. It also started happening with FS2004 and Trainz simulators. I replaced my video card and power supply with used ones that I had on hand with no change what-so-ever. I cleaned, polished and prayed with no positive results.
Finally, while rebooting one time it gave me 5 beeps which normally means a processor and/or mother board going bad. While trying "one more time for good luck" I got a weird screatching noise in the form of burps from my speakers. Wondering if that had anything to do with it I went into the BIOS and disabled the on-board speakers. No audio but no more rebooting either. All my simulators worked perfectly again.
I then got out the CD for my mother board and reinstalled the drivers for the audio. I am now back in business.
Mother board: ....SOYO DRAGON 2 K7V880-4AP1 Socket A (462)....
Something to think about if you happen to hear of someone having this same problem.