I might stay away from any 64 bit operating system now. If you want Vista, get 32 bit instead of 64. But I just use XP Media Center Edition 2005, and it works. Yes, when you overclock your q6600, your RAM speed will go up. But you'll have to make sure your RAM doesn't speed up too much, or the system wont boot, so you'll have to mess with the RAM divider in your BIOS. But you'll figure it all out once you have your rig.