I used FileSort to move a large group of files around based on the filename.

Windows is slow/unresponsive accessing the folder because every file extension has to be checked to determine the icon. If you have an active virus scanner running it can slow this down a lot. I'm not sure how your trying to move the files but if you select a group of files in the folder and then right click on the selected group windows again has to check every file extension to determine what options you will get. The more programs that you've installed that add shell extensions the more this will slow this down.