Bart, try "help rmdir" and you'll get the following:
Removes (deletes) a directory.
RMDIR [/S] [/Q] [drive:]path
RD [/S] [/Q] [drive:]path
/S Removes all directories and files in the specified directory
in addition to the directory itself. Used to remove a
directory
tree.
/Q Quiet mode, do not ask if ok to remove a directory tree with /S
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I think your problem is that you put the switch at the END of the
command, instead of the beginning, i.e.,
rmdir /s c:\windows\folder