[guygee]

If you google "Explorer at 99%", you will get numerous hits in forums where other people have had the same problem. At least one suggestion that seemed to be worth a try:

If a virus or other malware is causing the problem, it is most likely hiding in your system somewhere and being installed at boot-up to infect explorer. You want to restart an uninfected instance of explorer. Try bringing up Windows Task Manager, and in the "Applications" tab click on "New Task" and type in "explorer".. That should restart explorer. At this point you will be able to run anti-spyware and virus detection programs, or run HijackThis and have diggrd examine the entrails.
OR...
If it appears that files are missing from your current hard drive, personally I would pull the drive immediately, buy a new one and reinstall the OS. Next I would put the old hard drive into a Firewire/USB external enclosure and run a good file recovery program to try and save my data.

Hope this helps...