Gary
Looks like this is a server configuration setting, I can't delete any of mine, either. They probably don't want people going in and deleting files from their gallery, as it would leave broken links in the threads that referenced them. Like miamirick said, if you really need to get rid of some you should ask an admin, maybe they'll do it.
miamirick
LOL, I thought that was an image of an old Kaypro at first, brought back some bad memories.