I was struggling here trying to delete 2 folders that contained an enormous number of subfolders and I was always getting a "too deep folder" or "file to long" errors.
After some search and testing here's a nice, very nice solution for doing it from command line with Robocopy:
- Create an empty folder (ex.: D:\Empty)
- robocopy /purge D:\Empty D:\longfoldername
And it's done! :)