I am reformatting a HP computer which came preinstalled with xp home but the owner has no disk.It has a valid key which is on the side of the computer case and I am using my oem copy of xp which I got off newegg.All is well until it ask for the serial key.Enter it and it says it's invalid.I am entering it correctly and my copy of xp is legit.I have went thru the whole reformat twice and get the samething.Not trying to scam or anything like that but just trying to work around a lost cd so what would the problem be here?The key on the HP computer is an oem key and my copy of xp is oem.