Unfortunate for you that cd key is worth less at this time. With you Win Xp disc corrupt there is no way to install. It is hard to get a new disc for free. There may be some site that offer free download s of Win Xp but be ware. These have a lot if trash in them Microsoft wants you to buy another one. They cannot just give the system away. You can try and clean that disc real good and maybe it will start for you.