Reformat. Quick and easy. Sounds like it is very probable it is just a software issue. If that doesn't do the trick, then you know it is likely hardware.

It is unfortunate you don't have the disks, that makes things more a bit more complicated but it still isn't that complicated. Window XP's generic drivers are pretty good, but you probably want to go grab the latest XP drivers for at least your graphics card, mouse, sound card, and network adapter. XP disks aren't too hard to get your hands on.

In reality, a little bit of time and without spending a penny, you have a chance of getting it running as good as new. Of course, that is as good as new for a six year old laptop.