You should by now be running the RC release of Windows 7, which is publically available with free validation keys given by Microsoft that will work fully till sometime in 2010 (March I think).
It's very close to the final release that will come soon and sorts out quite a few bugs in previous versions. The build number is 7100.
Program Files is the directory where the programs install in Windows 7 and Vista, just like in XP, yup.
Try the new OS build, Nvidia will have better working drivers for it and see how it goes. If things work as expected you'll actually find the game to run faster in Windows 7 than in Windows XP.
