Due to a "wormable" security hole in XP, 7, and related Servers (although it isn't being exploited yet) Woody's urgent recommendation is:
MS-DEFCON 3: Get Windows XP, Win7 and associated Servers patched
For XP and 7 users, I’m moving to MS-DEFCON 3: Patch reliability is unclear, but widespread attacks make patching prudent. Go ahead and patch, but watch out for potential problems.