I still have Windows 2000.... best ever (for me) but maybe useless for you.
I actively use Windows XP (off line) on 2 tower PCs, have Windows 7 on one laptop and one Macbook Air. The latter is the only system that never fell over (yet) except for W2000.
I have all Windows O/S disks from the year zero. Anything above 7 I won't touch... just yet.
