I have two different copies of Windows 7 installed on two separate drives and use Easy BCD to add an entry to the copy connected to SATA port 1. That way, when I start my computer up, I have the choice of which OS to load. I was able to do the same thing with Windows 8 comsumer release when I wanted to try it out. The biggest reason I like to keep different OSs on separate drives is because it makes system imaging much neater, and also if one drive fails for some reason, or gets infected by malware, then I have the other drive to fall back on. The instructions for installing either 32 bit, or 64 bit should be the same, as far as I am aware. At least I have never seen any difference when installing either version on my PC's