Tried System Restore?
Dr Watson is the debugging tool for Windows, if it pops up occasionally after a problem that's normal, if it keeps appearing and your machine is not working properly, then something is wrong.
Remove and re-install your USB device drivers; unplug all USB devices, go to COntrol Panel/System, Hardware Tab, click Device Manager, right click every entry under USB controllers and select Uninstall. Reboot, have your XP CD handy. Allow Windows to reinstall USBs, you may need to reboot before plugging any devices in again.