I am trying to delete a folder on an external hard disk that was created on another computer. First it tells me that I need administrator permissions to modify it, which I grant. Then it tells me that I need permission from dougal\robert to do so, dougal\robert being my own user account on the machine I am using. I have given full control in the security settings both to administrators and myself, but nothing will enable me to delete this folder. How do I get rid of the thing?