How can I delete a folder from my external hard drive?

How can I delete a folder from my external hard drive?There is a folder on my external hard drive which can't be deleted. Every time I attempt to delete it I get an error message which says "You need permission to perform this action.You require permission from S-1-5-21-329068152-113007714-1060284298-500 to make changes to this folder" Does anybody have any ideas? I'd be really grateful!