How often do computers sync their clock with a domain controller - by default? Or where is this option located on windows 2003?
You can check the setting from an elevated command prompt with w32tm /query /configuration
NTP sync with the parent is controlled with the parameter 'SpecialPollInterval'. Its value is in seconds. The default values of SpecialPoll for any member of a domain is 3,600 (60 Minutes). For non-domain systems, it's 104800 (7 days).
SpecialPollInterval is ignored by default, and a 'floating' value is used which is adjusted automatically based on the perceived stability of the time source. To use the fixed value in SpecialPollInterval, the source list of NTP sources (the 'NtpServer' line returned by the query above) must have the ,0x1 flag set at the end.
Much of this is detailed in this article: http://support.microsoft.com/kb/816042