If you are tring to activate a copy of Windows 7, but cannot because it was on a different PC, there may be a solution. If the prior computer came with windows 7 pre installed you are out of luck. If you bought a copy of windows 7 and installed it on a computer and now want to install it on antother computer, this is what you must do. Uninstall windows 7 from the first computer. Install in the second. When you are asked for the key number do not give it. In addition, make sure that the box authorizing automatic activation after install if not checked. After you are installed try to activate. If you cannot you will be given a phone number, call it and activate. If still a problem, a rep will come on the phone to help you. If you tell him the history of the Windows 7, in question, and that it is not on any other computer, he will activate you.