OK, I've got it.
I don't know why booting my booting image is using 1280x1024, pal-interlaced but what I've done is to adjust that mode, changing it to lines (with lines now it isn't crushed anymore) and v-offset to 40, so now I've got the booting image with that (perfect, full screen without borders and centered), and later it uses HighGFX 1024x768, just the same (full screen, no borders...). So now it would be just to try to get a full screen of the games and so, that I must try to change (I think they are 800x600).
Really this config tool is very complete. I think it must be, as there are a lot of Tv's and modes, so surely a lot of them must be adjusted manually.
Last edited by Retrofan; 02 April 2013 at 03:39.