I had the same problem (explorer.exe staying at 100% CPU) and for the same reason (corrupt .avi file). I moved all the new files with no thumbnail into a special folder to more easily weed out the corrupt file. Surprisingly, the main video download folder still hung when it was displaying thumbnails and explorer.exe stayed stuck at 50% cpu without ever dropping.

So I closed explorer.exe started it again, went back to my main video download folder, switched to "list view", sorted the files by "modified by", and started going through them one by one with Task Manager open, looking for the one that made explorer.exe jump. None of the recent files caused explorer.exe to jump so I was stumped.

I decided to jump ahead to the folder with the video files without thumbnails (one of which I assumed was corrupt) in "list view". This folder only contained about 50 files versus the 1000+ in my main video download folder. I easily located the corrupt avi file with the process mentioned in the above post (btw, the filename was preceded by TMP in case that is a flag).

Then I went back to my main video download folder, switched to "thumbnail view" and sure enough, everything was OK.

The reason why the main video download library was causing explorer.exe to hang even though there were no corrupt files in the folder I moved the suspect files to was a subfolder of my main video download library. I am guessing that explorer.exe takes a quick peek inside subfolders and a root folder can hang if a corrupt avi file is found in a subfolder. This is just a guess.

Given this, it would better to move the suspect files (files without thumbnails) to a folder in the root directory, then follow the process above to locate the corrupt file, then, after deleting the corrupt file, move the remaining files back to the proper folder.

HP