With some kinds of problems--- missing or overwritten system, files, for example--- a reinstall of windows over the top of itself may completely cure what's wrong, and can do so without losing your data, your installed apps, or any customizations or alterations you've made.

While that advice is deliberately general, a targeted kind of fix for problems associated with a copy of Explorer that's gone bad might be an easier and quicker solution. Try putting in fresh copies of explorer.exe, shell32.dll and user.exe: In combination... fresh, known-to-be-good copies of these files may solve many problems with Windows Explorer.

Those fresh copies are on your ME CD....however, I don't know if you have a separate cd or just a restore disk, so more information is needed before good advice here can be given. If you have a separate CD, let us know so we can help you extract a new copy of this file from the cd to your harddrive to overwrite one that is possibly corrupt.