I'll make life easier for you dude since everyone is just confusing you.
If the DVD your making is 4:3 ratio (not many are these days) then make your background image 800x600 (800 wide x 600 height)
If your DVD is WIDESCREEN 16:9 then make it 848x480 (thats 848 width)
There. Why do people try and over complicate things and confuse people who are asking for help? doh!