WHEN EVER I TRY DO DOWNLOAD ANY UNIT CREATING TOOL IT ASKS WHAT I WANT TO OPEN IT WITH. NOTHING I HAVE TRIED WORKS. I HAVE TRIED SAVING IT BUT THEN WHEN I GO TO OPEN IT UP IT UP IT ASKS WHAT PROGRAM I WANT TO OPEN IT WITH AGAIN.THIS ALSO HAPPENS WHEN I TRY TO DOWNLOAD MODS. HELP