Como deixar seu Mugen em FullScreen

Etapa 1 

Para começar vá ate a pasta "Data" de seu MUGEN, e abra o arquivo " mugen.cfg ".

Etapa 2

Após abrir este arquivo procure a linha "[Video Win]". Nessa linha tem vários itens de configuração sobre vídeo de seu MUGEN. Para que ele abra em Tela cheia e bem simples.

Repare nessa linha:

;Set this parameter to 0 to disable screen stretching, and set it to 1 if

;you want to scale it up to fit the current resolution.

Stretch = 0

Etapa 3

Troque esse 0 por 1 , Logo abaixo, terá uma explicação na língua inglesa dessa maneira :

;DirectX mode

;Choose from Hardware, Software, Windowed, Overlay, Safe and None

;Hardware and Software run in full-screen. Windowed and Overlay

;run in a window. The windowed modes require you to set Depth to

;whatever color depth you are using for you desktop. The best results

;are when you run in 16-bit color. There is no advantage to running

;in 32-bit color. If Hardware, Software and Windowed fail, try Safe.

;None uses GDI to draw, so it's very slow. Use None only if

;you cannot get anything else to work.

;Overlay is not supported by all video cards, but can be faster than

;Windowed if it works.

DXmode = windowed

Etapa 4

Bom, você deve ter notado a linha  DXmode = windowed . Agora troque o windowed, por fullscreen.

Ficará assim :

;DirectX mode

;Choose from Hardware, Software, Windowed, Overlay, Safe and None

;Hardware and Software run in full-screen. Windowed and Overlay

;run in a window. The windowed modes require you to set Depth to

;whatever color depth you are using for you desktop. The best results

;are when you run in 16-bit color. There is no advantage to running

;in 32-bit color. If Hardware, Software and Windowed fail, try Safe.

;None uses GDI to draw, so it's very slow. Use None only if

;you cannot get anything else to work.

;Overlay is not supported by all video cards, but can be faster than

;Windowed if it works.

DXmode = fullscreen

salve e é só testar