There is a real time clock on the motherboard that is a nickel dime affair that can do that when the "battery" gets low. What most do today is to let Windows update the time when they are on the internet. Here's how -> http://www.boulder.nist.gov/timefreq/service/pdf/win2000xp.pdf
I use Windows XP home edition. Just within the past week my computer clock has been losing time. I have to keep resetting it and it's becoming a pain in the tushy. My computer is on for most of the day and night. I do put it in "stand by" mode when taking a 2-4 hour break. Not sure what other information you may need. Any help would be appreciated. Thank you.
Prickly Pear (Ellie)