What happens when you discover your copy of Windows is invalid? You probably will get a Windows Genuine Advantage (WGA) notification informing you that you're illegal, and you need to purchase a legal license. If you search the net and Microsoft's web site for a way to activate your copy with a legal key you purchased, you may find yourself in a bit of a mess. You see, it isn't terribly obvious that you CAN in fact simply activate Windows XP, Vista, and Windows 7 with a new legal key - and without reinstalling anything at all. Finding the information on how to do this is rather difficult, and I'm not sure why. Not to worry though - it's a piece of cake!