Planet M.U.L.E.

Whenever I hit the fullscreen button it goes into fullscreen mode, but the actual screen is the same size as when not in fullscreen mode. The grey border/HUD thing expands to full, but not the game screen proper.

Hit F5 And Then It Will Show only Game

I think what he means is - the game doesn't scale to fill the screen.  It simply creates white-space AROUND the game.

I Know. It Makes The Game Fill Up Entire Screen

I suggest you try to update your graphics drivers. What operating system and screen resolution do you use?

I have the same problem on Mac OS 10.6 Snow Leopard, frame expands to fill the screen but the game does not zoom to fill it, I only have empty black space around it and can't see whole game screen.  MacBook Pro 2.4 GHz Core 2 Duo, 4GB RAM, NVIDIA GeForce 8600M GT w/ 256MB VRAM

I also see this effect, the game goes full screen and actually gets bigger (i.e. zooms in) and it looks fine. It just doesn't go to the 'very' edges of the screen, I have about a 1 1/2 inch border on the top and bottom, and about 3 inches on the sides.  I have a wide-screen monitor so this may be the issue, I also run in a high resolution 1920 by 1200 pixels...

EDIT:
I tried several different resolutions from 800X600 and everything in between, all the way up to 1920X1200 and the full screen mode looksexactly the same at all resolutions.

MULE on Atari800Win looks better than Planet Mule in full screen mode. Try it and youll see! :o)

My MULE is not even close to full screen and there is nothing wrong with my drivers. It is about 4x the area of the original screen. It is big enough but there is so much room around it, there should be chat to the right side or something.