Clock on XP machine is wrong

The clock on this machine appears to have a mind of its own. I have heard of the clock slowing down where in fact you would replace the CMOS battery. But this clock is weird I will shut down every day and boot back up with the correct time, but say the 3rd or 4th day the time will be drastically out. By a least a day. I checked the CMOS time and unplugged the computer and wait five minutes. When the computer was rebooted the CMOS time was five minutes behind. It doesn't sound like a typical CMOS problem but the clock is still losing time. Any help in this matter would be greatly appreciated. Thanks.

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Have you tried these steps on the microsoft website?
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/windows_date_it_overview.mspx?mfr=true

I had this problem on both a desktop and a laptop. I replaced the CMOS battery and everything was fine.

I have had this problem this in the past before with windows xp and 7.
as a technician my first recommendation is to replace the cmos battery if that doesn't do the trick, then go into regional and language under control panel and verify that you have the right country for the current location then go out to date & time and make sure that you have the right Time Zone selected.