TFT Monitor: Large Border with DOS

I have a big problem:
Yesterday i thought it would be nice to play some old DOS-RPGs.
So I downloaded DOSBox installed the games and played.
The only problem is that my TFT-Monitor (shitty Targa P11...) show me a fat
coloured border arround the DOS window. (image: http://img99.imageshack.us/img99/669/fuck0mx.jpg).
What can I do against it??

See if there's a setting in the monitor's menu to turn scaling on or off for non-native resolutions.

no, there isn't ...
the same problem occours while booting

ok fix'd it. more or less.
fullfixed=false --> true

Tee eff tee.... Wow so kewl.