[Preamble: I am on Mac and I've ported my favorite program to Mono, mostly... but I'm beginning to give up on its implementation of Winforms. It's surely very impressive and has been the result of a massive amount of work, but when you get deep into the details, it's quite different. And getting it working perfectly on OSX will be a huge task]
As a guest in VirtualBox, what is the lightest weight Windows I can run that will run .Net 2.0? I am also interested in programs to lighten up Windows... I don't need a lot of its functionality.