Fuck me running, I never thought of that. If you use an nvidia card you can set up hotkeys to control pretty much all of the driver functions. I just set CTRL-ALT-Right Arrow to toggle between the two. Thanks for pointing this out!
Yeah, nvidia cards are cool like that. A suitably recent driver will let you tate your screen. Of course it's rather pointless for mame, which wil let you tate it anyway if you want, but for windowed windows applications, it's quite handy. if you have a tatable monitor, you can run windowed vertical shooters at a hgher resolution.