BTW, if you're testing two (or more) display modes frequently, you may want to take a look at my freeware utility, QuickerRes. QuickerRes lets you assign hotkeys to display modes, and also a hotkey to switch back to the last mode you used. This lets you easily switch back and forth between two modes with a single keystroke (I use Ctrl+Shift+Z).

You can find QuickerRes at http://www.mWilden.com/QuickerRes/.