Unable to get Updates from Windows update!!

I bought a copy of XP Pro from an auction site, it had a product key after installation I can’t get the version validated through Winows Update Genuine software procees. I get a invalid volume licensing, I reported the transaction to both the auction site (they kicked the seller Off site)and to Microsoft but they never answered. MS had a deal to report illegitimite pirating of XP, saying they’d give you a valid product key but reniged on thee deal. does anyone know of a way to get around this Genuine software validation process?