SP3, and maybe the RyanVM Post-SP3 update pack to minimize the amount of updates needed.
If only ReactOS was ready for the big time -
http://www.reactos.org/en/index.html
This is NOT Linux + Wine, though it does have a synergistic relationship with Wine.
It is still, as they say, not feature complete, though some applications can be run, but in terms of feature completeness, Linux + Wine probably has a major edge on it at the moment.