Open up the MS-DOS command prompt and type this code

C: 'or whatever your drive letter is for the folders
cd\ 'this gets you to the root
dir/s/b > files.txt 'this will put your whole file list in a the file (will take a while)

Next open the file (Drive:\files.txt) in Excel and use =len(A1) in column B and sort it by that column, blah blah. I think you can get it from here.