I would like to play a few games on my iMac (mid 2007 Alu, with the HD 2600 Pro, 2.4 GHz C2D and 3 GB RAM). I'm mostly looking at The Orange Box, though I might get some other titles like Mass Effect and Bioshock, some older games as well as Starcraft 2 in the future. I can buy Vista Home Basic 32-bit, Vista Home Basic 64-bit and XP Home Edition 32-bit for exactly the same price and I've been wondering which one I should get. The Windows installation will only be used for gaming for now, although I might use it for some light Windows-only tasks like video chat over Windows Live Messenger. So, which of those three versions of Windows will give me the best gaming performance?