I've noticed that when using this command on a windows platform you may encounter a permissions error which may seem unwarranted. This commonly occurs if you are or were using a program to edit something in the to be deleted folder and either the item is still in the folder or the program that was accessing the file in that folder is still running(causing it to hold onto the folder).
SO... if you get a permissions error and there shouldn't be an issue with folder permissions check if there are files in there then check if there is a program running that is or was using a file that was in that folder and kill it.