Windows Vista, which you need to de-vistaize in order to get something productive out of it... Im on a mac now, and like it, but as someone else said before, xp and win 2000 are not bad at all.
Office 2007, nuff said....
3DStudio Max, while powerful, i never liked the whole parametric thing...
Itunes on windows. On a mac is ok, but on a pc is slooooowwwww
Windows Media Player. You have to right click to find how to do something simple, actually anything...
Archicad on teamwork. While regular archicad is ok, the whole teamwork thing makes no sense...