Excellent point Murasami!!! See this: http://www.gnutellaforums.com/showth...9587#post99587
Oh I just realise that link doesn't apply here. But Murasami's suggestion is extremely valid. I think somewhere you can reveal whole extension names but I don't know/can't remember how. Ask a windows user!

You could also try duplicating the file (as a back up) & manually typing in the zip extension.

Or (as well as making a backup) as 10904org suggested go to Properties & add details there.