Hey, I just finished my computer build (thanks to all the advice from this forum, especially MadAdmiral). My question now is that I want to purchase a copy of Windows 7 64-bit. I've seen a few "used" ones on ebay. Even ones that say they've used the 32 bit but not the 64-bit. Do you think I can use these? I would think Bill Gates would have something in place not to let the user load it a second time.