Wish I had a suggestion for you but I don't. Maybe take it to a repair shop and let them test your hardware. Could be a video card problem. With the age of the computer I don't know if it would be worth the money. You can get a new laptop running XP for less than $500 these days. The repair shop would probably charge a couple of hundred if it's fixable and you'd still have an outdated OS and hardware.
At this point I would do something daring like re-installing WIN98. From what I remember if during the re-install it finds newer files it will prompt you not to install the old ones.
Or you can buy some bricks and meet me outside Bill's house. It took me a week after my upgrade to XP to get my sound card working again. I finally downloaded a NT driver for it.