Need permission from myself to delete a folder but I can't get it

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?

Thanks. I'll try File Assassin next time.

In this case I can't remember every single step I took, but one thing I did was to change the ownership of the folder in the security advanced settings from myself to myself and to apply that to all subfolders and files. This ensured that all files and subfolders had the same ownership as the parent. I also had to disable inheritance for my user permissions so that the permissions for the folder I was trying to delete were independent of the parent folder. Then it worked.