Yes, I tried TVOverScan options, but it didn't works.
I've been working on it, and i have more info. When I use progressive signal, the dot matrix of the xserver looks quite good. When in use interlaced signal, dot matrix looks worst. That's the reason I think that the best mode (at least for me) is with progressive.
The problem with progressive it's that I can use only two modes: 640x480 and 720x576. With 640x480 I see the complete desktop. If I use 720x576, I get the problem of my first post: desktop looks like "zoomed in". When I set 800x600, I only get a black screen. But my TV receives the signal and says that is 720x576p, but I only see a black screen.
With interlaced mode, i can use 800x600 and 1024x768, but image it's not so clear.
I have attached the xorg log with verbose mode. HD576p with 800x600 should work, isn't it? My graphic card it's built onboard, so i share ram memory. Progressive signal needs more memory than interlaced? I'm afraid I don't know very much about video output.
Why I get the black screen? It's a bug? Anyone have any idea? All answers are well received, I'm a bit desperate
PD: I also include my xorg.conf