the files in the _restore/archive dir are marked hidden/system/read only. You will need to use a third party utility to remove them. I'm not positive, but I think that Power Desk can see that directory when set to "show all files". I have also used a utility that comes with DR DOS called XDEL. It can delete HSR files using the /r switch. (type xdel /? to see the list of options).
I think you can still download DR DOS (free for personal use), but I've forgotten the web site and since they don't have a link to it on their regular pages, you have to use ftp to get it. I might be able to send XDEL to you as an attachment to email.
.bh.