Click start then run, type sfc /scannow then press enter, you need the XP CD and Windows File Protection will show a blue onscreen progress bar, when 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.
Windows will appear to load normally then either the monitor will show progress or the screen will go blank, do not disturb this. This will take an hour or so before it gets to the desktop.
Click start, all programmes, accessories, system tools to run disc clean up, click more options then clean up restore points, click confirm, click OK. Then from system tools, run disc defragmenter.
Click start then run, type prefetch then press enter, click edit then select all, right click any file then click delete, confirm delete, then reboot
When it gets to the desktop, the system files and the hard drive will be as they should and you can check for any improvement