See http://support.microsoft.com/kb/950527 for the ConfigMgr 2007 hotfix that adds new supported platform entries for:
- Windows Vista Service Pack 1 (SP1)
- Windows Server 2008
- Windows Server 2003 Service Pack 2 (SP2)
- Windows XP Service Pack 3 (SP3)
These changes should be included in ConfigMgr SP1 too, so you can choose to wait for that too.
A separate hotfix for SMS 2003 SP3 should be available in the near future.