actually my friend bought this used lap top from a pawn shop is the windows os legal? How can you tell? Also they provided a user password for the XP Pro OS but not an Admin password. Will Microsoft help? He has the reciept and he can't get his money back. It boots, but has 25 viruses of all sorts on it.
There's a Microsoft geniune validation tool (or something like that) that checks if your windows is legit or not.
One thing I would recommend to your friend, if he has a copy of his own windows and no relevant data on the HDD. Reformat the whole thing, start fresh, install everything yourself and you'll be able to reset all the passwords + get rid of viruses.