I tried to set the video mode to 12h (640x480 VGA) and saw all distorted characters. I am using a 17" LCD Screen and my windows display properties refuses to go below 800x600 Is it possible to use 600x800 display from the native BIOS routines or diaplay 640x480 on an LCD?
If your Windows properties won't go below 800x600, it sounds likely that the monitor doesn't support that mode?. You can certainly use 800x600 from DOS, but you will probably have to write your own driver routines?, unless your compiler includes a suitable library for your specific card, or at least the mode it uses. The Borland compilers used to provide BGI's (Borland Graphics Engine) files which actually drove the video card.
Depends on the monitor, some have better scaleing circuits than others and yours may not be able to scale from to that particular resolution. Need to check the manul for your monitor.
I don't believe that the monitor is the problem in this case. I think it's far more likely he isn't programming the graphics card correctly. If you try to get a modern TFT monitor to display a mode it doen't like its onscreen display will display an error message.