First of all, thanks for all the replies.
Hell yeah. We are trying to make this on XP, but we tried it in dos too, but its the same.
The main problem is that on my friends videocard ( nvidia geforce 6800 ) we cannot put even a pixel out in higher VESA resolutions than 640*480.
The simplest code we tried was this and it did not work of course ( on his pc ):
Code:
asm
  mov ax,4f02h
  mov bx,11bh
  int 10h
  mov ax,0a000h
  mov es,ax
  mov cx,32768
  xor di,di
  mov ax,0ffffh
  rep stosw
end;
But it still does not work. He has a blind screen.
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But my other problem is that the way cronodragon mentioned is a bit slow. I made a unit the same way, gonna post it in my next post...