If you are running Microsoft Exchange in your organization and are in the US please be aware that there is a hotfix for the daylight savings time change.
For Exchange Server 2003 SP1 the fix is at:
If you are running Exchage Server 2003 SP2 the fix is at:
This fix must be in place by March 11, 2007.
If you do not install this fix your users will be an hour early for every appointment they have for 3 weeks until Outlook catches up. (which could be considered a good thing I guess if you have chronically late users I guess) ; )
There are several other Microsoft Products that need to be updated. Check this article from Microsoft to see what you need to do and if your product is affected:
There is also an article on how to fix and configure DST via the registry at: