sounds like a ram module going bad, a faulty power supply, or your CMOS is dying. Does you time ever become way off? Do you ever get any errors?

THis is a tough problem to work out... I'd try checking all of my hardware first. Make sure everything is working properly..
Also, do a virus scan just to make sure you havent picked up some wacky virus....

Further, I'd try a system restore to see if that corrects the problem. What programs are running during this "refresh"?
This could be a program related problem. Perhaps windows is crashing from some faulty program, and is attempting to recover itself...
Try removing all programs running in the background and run your PC for a while and see if you still get the same results. If so, then it might be time for a format... and reinstall XP.

Let us know how you get on!
BB