Jammy i hate to tell you this but a XP home/pro disc and a re installation disc are two totally different types, the first one is the operating system and the second one just resets everything as if youve just formatted the drive and put a fresh copy of the XP on the drive!
if the seller has sold u it as a "OEM copy of XP Pro" but it turns out its a Reinstalation disc they have sent you either the wrong disc in which i would get back to them and demand they send you what they sold you! or Grill them on the feedback and cancel the payment!
Let us know what happens! shame really ive just given two copies of XP Pro away to a person i dont really know!