I have a similar issue, having just acquired (and successfully installed) FSX on my Dell, I found that during the initial set up of a flight (Flight Planner, Weather etc) the screen res stayed as it was but when I finally hit Fly Now, it decided to change the resolution and gave me the 2D cockpit with black bars either side of it. However when cycling through the other views, the screen res stayed as it normally is (1366 x 768 and yes it's a laptop until I can upgrade my desktop again).
Any way of getting the 2D cockpit back to full screen? Never had this problem with FS9 on the XP desktop, which has considerably less power than the laptop in all areas.
