Gnome + screen resolution + no monitor
I'm using Gnome, Debian. PIII 866 MHz, 512 MB RAM, Intel 815...
Everything work's fine except one thing, when monitor is not attached to VGA, screen resolution is 640x480 (I know that because I'm using TightVNC) whenever I try to connect through VNC. I need at least 800x600 but it won't let me change
How can I solve this?