Bios/cmos date

[Woodman]

Intel P4/1.6 - Intel D845BG mobo - Intel bios - Windows XP Home - Alpha UPS.

I disabled the auto internet time sync feature in XP and now find that the clock is fast by about 30 secs per week.   I know it's the wrong way round if the cmos battery needs to be replaced but it was replaced and made no difference, the time still gets ahead of itself.

OK it's no big deal, am not running any time-dependent programs, it's just boldoy baffling.   Could the 'problem' be caused by a variation in the mains power voltage or frequency, I understood the psu would take care of those?  The UPS gives no 'out of range' indication.

Thanks

[patio]

Windows has time keeping errors.
If everything else is running fine i wouldn't be concerned.
The CMOS battery keeps the system time and has no effect on Windows.

I use the wall clock...