Re: Messed up lappy...
Sounds like there's more issues there than just a resolution change. Try doing a repair install for XP, you'll need the XP installation disk.
First though try booting into safe mode (usually hit f8 for extra boot options) and uninstall your graphics drivers if you can.
"As a result of all this hardship, dirt, thirst, and wombats, you would expect Australians to be a sour lot. Instead, they are genial, jolly, cheerful, and always willing to share a kind word with a stranger, unless they are an American." -- Douglas Adams