FIXED, I guess.
Well, this thing is buggy.
I found Aspect in the Picture menu but it was greyed out for HDMI input.
I selected the TV tuner and Aspect was accesible with some options I don't recall.
I went back to HDMI and sudenlly the Aspect option was now accesible. It has the following options: 4:3, 16:9 (wich is the one selected), zoom 1 which makes the image even bigger, zoom 2 which makes the image huge, and PC mode.
In PC Mode the image seems to fit perfect on the screen. I will do further testing and let you know if I still have problems, but it seems fixed.
Thank you people.
Anyhow if someone knows how to get into the service menu, please tell.
CH!