Disable New Folder Button in a Document Library

Hi, 

i Need to Disable New Folder Button in a Document Library.

Trying out this feature:

http://jassimkhan.blogspot.com/2010/10/sharepoint-2010-disable-new-folder.html

When i try and activate the feature with "stsadm -o installfeature -name DisableNewFolderButton"

i get this message:

Required attribute 'Id' is missing from tag 'Feature' in feature definition for feature with ID '00000000-0000

-0000-0000-000000000000'.

What am i doing wrong?