To check for a couple of things, click start, all programmes, accessories, system tools to run disc clean up, then from system tools, run disc defragmenter.
Click start then run, type sfc /scannow then press enter, you need the XP CD and get a blue bar, after the bar goes, reboot.
Click start then run, type chkdsk /f /r then press enter, type Y to confirm for next boot, press enter then reboot.
It will appear to load normally then either the monitor will show progress or the screen will go blank, do not disturb this when it get to the desktop, the system files and the hard drive will be as they should
It may have been looking for files from a programme you have uninstalled