When I turn my computer off then on my clock always wrong. It is 3 hours behind - always. I replaced the battery, but this did not help. Any suggestions?

Check to see if the clock in BIOS is also incorrect. If it is, then the BIOS clock may be defective, and this is where the Windows clock gets its time.

If the BIOS clock is correct, then see if disabling all screensavers, and power management in BIOS and in Windows helps.
If not, then do a clean boot to troubleshoot it.

Every time I've installed Windows, it's defaulted to Pacific time zone. So...

If you live in the Eastern time zone, AND if you're running software to automatically update your computer's time from an internet server (such software is included in XP), AND if Windows was never changed from the default Pacific time zone (it happens often - many people just make sure the time and date are correct at that point in the install), that would account for why your computer is always three hours behind.