Hijack This http://mjc1.com/mirror/hjt/
Make a special folder to download it to. Set it to "Scan" and then to create its "Log". This will be long, but copy all of it into Notepad and post it to be checked.
I have a similar problem here at work with Win2K workstations.
1. Web response gets VERY sluggish.
2. IE uses 99% of CPU resources.
3. When I checked Tools-->Options-->Settings, the current location for temporary internet files was blank, and the amount of disk space to use for disk cache was zero.
4. Couldn't reset the amount of disk space without getting "Please select a value between 1 and 0 for how much disk space temporary internet files may use."
5. Couldn't change the location without getting, "There won't be enough space in the new location for the currently downloaded content. Please either delete these files first and try again, reduce the size of the folder, or pick another location." Plenty of space on the disk.
The only way I could rectify it was to delete the user's local profile and let it recreate itself the next time the user logged in.
No idea what could be causing it in XP, but figured I'd throw this out there.
I think you should run all the spyware removal programs in previous post.
Maybe your cache is overflowing.
This is the way to empty it in XP
1.Open an Explorer folder window (for example, double-click My Computer). From the Explorer menu select Tools | Folder Options | View. Make sure that you have checked the box next to "Show hidden files and folders" and uncheck "Hide protected operating system files".
2.Start Internet Explorer and click Tools / Internet Options / General tab / Settings / View Files.
3.IE should have opened up a folder window, typically viewing a folder with the name of C:\Windows\Temporary Internet Files. Put your cursor in the Address area of the folder window and add the name \content.ie5 to the name, so in our example the Address bar would now read c:\Windows\Temporary Internet Files\content.ie5.
4.You should see a series of four folders with random eight-character names like ADOZMZS1. Go into each folder and delete all the files they contain. Do not delete the folders.