My desktop computer came originally with windows me. Several years ago I got windows xp professional version that gradually was updated by Microsoft to sp3. Few weeks ago my pc didn't want to boot, probably I got virus, and I couldn't find my windows xp disc. I turned up entire house but it never showed up. I bought online another disc – windows xp sp2 home edition. I loaded it to my pc but Microsoft tells me that coa is invalid. I entered the production key that come with this disc several times and each time I got invalid key. Is there any help with the production key? Is there a way to activate my windows xp disc? Please help.