problem with panel size

I'm having a strange problem with the panels for my aircraft. I've made a background that is 1024x768 but no matter what I do FS2004 scales it so it only cover about three quarters of the screen and the simview is only about one third of the screen. I even tried to copy the whole panel folder from one of the defaul aircrafts that I know work. But when used with my aircraft, even that panel had the same problem. What should I do? I haven't found anything about this problem anywhere.