This issue seems to have been experienced by other people, see here and here. No solution given though.
some troubleshooting tips:
- Is it correct that, just like in the link, it is only the year that changes (with month and day remaining correct)?
In that case, I'd say it can not be the battery. Moreover, you say you checked your battery, so I would rule out the battery as the cause. - As you say the date in the BIOS is correct (again a strong argument for ruling out the battery), the date must be modified during or after booting Windows XP. In that case it must be
- (a) because of an issue in either Windows XP itself, or
- (b) caused by some program you installed (intentionally or not), or
- (c) a wrongly configured NTP server that Windows uses to update the date and time.
Edit: following grawity's comment below, reason (c) seems not possible. - I think reason (a) is unlikely, so I'd rule that out initially.
- To check if it is because of reason (b): set the correct date and then restart in safe mode (without networking support), and see if the date is changed to 2005. If not, I'd say some program (perhaps recently installed) changes the date.
- To check for reason (c), go to the adjust date/time dialog box (e.g. double click the time in the task bar) and disable Internet time synchronisation (see here for some dialog boxes).
- If only reason (a) remains, perhaps you can try changing and resetting the date format in the regional settings (see this microsoft article)