You have a good question; can't remember if the single core 939's are 64 bit compatable, which is what you have. I don't recommend windows 7 unless you can find the files for vista on hp's website for your specific board. I tried windows 7 on an old hp 939 board recently, and it couldn't find the files for hp drivers. You'll need to use hp's website for any windows 7 files. Some older boards will load it just fine; some are a pain.