A guy made a topic about two operating systems and that made me remember you can do something like that. I have a 150GB C: Drive with Windows XP Home SP2 on it and a blank D: Drive with about 250GBs of HDD space on it, all it has is some stuff that was too big for my current HD (I'm gonna do a clean sweep on both drives if I decide to upgrade). Would I still be able to buy the Upgrade package of Vista even though I'm putting it on a new HDD without Windows XP on it prior? I still have the original XP CD and registration key and the like. Would it at all slow down my PC?