I have a Toshiba L455 laptop that I recently purchased from a friend. It is running Windows 7. However, I keep getting these messages about counterfeit software and I cannot accept any Windows Updates without a key. I have a valid copy of XP w/service pak 3 with a key that I'd like to install on this laptop. I did not get a disc with this laptop but it is my understanding that he formatted this by "installing factory defaults." I don't know all this computer language so I'd like some simple instructions. And no, I can't go back to my "friend" to get this problem fixed. Also, the XP disc I have was used on a desktop. Does that matter? Do I need a specific "laptop disc" of XP or does that matter?