jwl812
It sounds like the component normally present in the default software (image or restore CD) which Gateway provides with the machine, is not present when you load XP Pro from scratch. The component I am referring to relates somehow to activation. Unfortunately this is part of the problem when you purchase from companies like Dell, Gateway, etc. This is how they restrict or lock you in. Pretty much the same thing goes for their hardware. In many cases you are required to replace failed hardware with their hardware due to their non-standard or proprietary designs.
Have you made any changes to the hardware? If not, I would contact Gateway or even Microsoft to see if they might be able to help. Gateway might give you a hard time because you didn't use their restore CD however but who knows; you might get lucky.
Good Luck.
fast586