I have a dell dimension 4400. About 3 weeks ago my computer had a virus and i couldn't run windows, so i had to format it. I don't have the original XP cd so i borrowed my friends. I installed it but when i tried to activate it it said that the product key was already used, which was understandable because its not my cd. So i got the product key from the sticker on the side of my computer, which should have been the original one but it says that the product key is not correct. Any idea what i can do? Thanks!