if you can i would save everything you can to disc that you want saving and then do a fresh claen install of your XP. as to be honest a fresh clean install is the best thing you can do, and by the sounds of it you seem to ahve a few problems with your file allocation.
atleast with your new install you will have a good running OS. if you do that and then reinstall all yoyu drivers and updates you should get yourself Norton Ghost do an image of your OS that way in the future if you have any problems that need serous attention you can just ghost your image over and you are back to new again
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