Explorer Lags in certain folders

I'm having a problem with explorer lagging terribly while viewing a folder of about 100 large video files in it. Scrolling up and down and just clicking the names of files causes the explorer process to use ~30% processor and activates the gray progress bar at the top behind the address bar (running classic theme). I moved half of the files to a different folder, and both folders exhibited the same behavior. I've turned off search indexing for the drive, and it doesn't seem to do the same in a folder of hundreds of non-video items on the same drive. Any ideas what's making it so slow?

Vista Ultimate 64 bit.
Two AMD FX-70s @ 2.6ghz
4Gb Ram
1950XTX