Window XP professional
service pack 3
pentium 4 2.66
2 gb memory

I had not turned on this computer for about three months due to problems. When I did go to Windows Update there were 30 of them. They all downloaded and ran. Everything was fine until I restarted the computer. The screen came up with a line that said CMOS Checksum error defaults loaded. Press F1 to continue. The start screen came up and I went to Windows Update. A screen came up that said date and time were out of sync with an update certificate. So I went into the control panel and corrected the date and time. It was way off like it said the year 2002. After I did this everything worked fine until the next day when I turned the computer on and I noticed the date and time were wrong again. Do I have a dead battery? If that is the problem what will happen if I take it out and replace it? If it is something else and you need more info let me know.

Thanks