I'd say try all that has been suggested, pefect disk, diskeeper etc...
If none of it works, then reinstall. A fresh install of XP will get rid of all that junk you have on your PC Lynch.. hehehe and it will give you time to download more junk to replace the old junk that you got rid of when you reinstalled.

You might try splitting your HDD into sections, 2 or more. One for the OS, and one for any files you download. That way you can defrag much more quickly, and I have found that you can use your OS to defrag the secondary and tertiary drives while surfing the net, etc.. providing you are not accessing those drives. But you have to stop using the default, in my case, the C: drive to defrag it, or it takes forever and your drive never becomes defragged... (that is my experience, others may have different results).
Perris seems to know pagefile, defragmentation and OS performance enhancement and the like very well. I would listen to his suggestions as they seem reasonable and quite well thought out.
BB