Solution that works
Ok, I had the same problem... installed windows xp pro sp2 exactly according to boot camp instructions... ran and installed the drivers off the mac drivers CD burned before doing anything, and it caused my macbook pro's keyboard and trackpad to stop working. fiddled around with this for a while to get it to finally work. if you go to control panel > add or remove programs, scroll down to the list of 'Windows Driver Package,' you need to remove/uninstall the three things: 2 of those entries say something like (aat***), which i can't tell you exactly how it's spelled because I got rid of them, and the third is something that says keymedia. One of the three says mouse, if that helps. You're basically uninstalling the keyboard, trackpad, and mouse drivers, and voila! everything works now. Trackpad and keyboard. It's perfect and doesn't affect anything else. So frustrating, but finally stumbled upon fixing it.
btw: plug in at least a usb mouse to carry this out. might be obvious, but probably should point it out.