My dad's birthday is soon and his PC is running the Windows Vista OS, so I plan on buying him the upgrade version of Windows 7 for his gift. The thing I was wondering is if I buy it for him; can I use the same copy to install it on my PC too? Now I already know officially(legally) the answer is no. I want to know if I can do it unofficially anyway. Basically my question is does Microsoft have preventative safeguards in place to detect and/or prevent me from using it on my PC after it is installed on his? I'm going going to buy him the upgrade either way, but if I can use the same copy to upgrade my OS I'll get him the Ultimate version. If not I get him the Home Premium version.