As you may or may not know, Windows XP provides an easy and fast way to synchronize your system time with an Internet time server (Control Panel/Date and Time/Internet Time). By default there are only two servers available (time.windows.com and time.nist.gov). To add more, just add them in the registry (HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DateTime\Servers).
More time servers can be found Here
