WHen I built my recent computer I bought a copy of windows xp x64 Oem. The problem that I'm having is that I wanted to jump on Vista as soon as I could and purchased a copy of XP MCE to upgrade to Vista Home Premium for free. My question is can I deactivate the copy of x64 that I have installed and give it to my sister or do I need to just suck it up and dual boot so I can upgrade to Vista. I feel like I've pretty much wasted a copy of xp if I can't and I really want to help my sis out right now. Any help would be appreciated.