I'm a
huge fan of Heroes of Might and Magic III, I always play as the Necropolis. There is nothing more satisfying than assualting your enemie's fortresses with catapults, balistas and 4-5K of armoured skeletons (with a few vampires and Ghost Dragons for good measure).
I went and bought a copy of the complete edition off Amazon fully optimised for Vista, but now I'm on 7. Figures.