Yeah, you can't "del" a directory, you should try to use "deltree" for directory and del for "files"
for example like this
@echo off
deltree c:\windows\desktop\newfol~1 /y (dos can read only 8 digits, whenever got spacing ot more characters will turn ~)
del c:\windows\desktop\file.exe ( is for deleting files not folder, and you don't have to /y cause it don't ask u)