As per your post... do you have the Gateway restore CD and have you tried using it? When you installed XP did you use an original copy of XP or a burnt copy or the recovery CD of 'another or different' laptop?
Based on what was posted so far, I am leaning towards doing a reinstall. So far I know is that you have restored back to the time prior to installing video drivers but since that did not solve the issue, I think you must consider doing a fresh install.
Without an existing recovery partition, you can use your XP install CD and drivers from the Gateway website. Another option is order a restore/recovery CD from Gateway (specific for your model)... which I believe is really needed and a good investment (they are reasonably priced, anyway -- like cheap
).