Ah, good old Age of Empires. :)
You can fit the window to scale as you want through the following command, From Ubuntu's Forum:
mplayer -vf scale -zoom -xy 600 my_file.avi
where -xy 600 is the x axis value. Replace the 600 with desired value you want. Also, you can enter the custom value directly into your mplayer's config file as stated:
you could also put in your ~/.mplayer/config file there are various ways to do it Code:
screenw=600
screenh=400
xy=.5
xy=600
and for fullscreen Code:
fs=1