I have an HDTV that I'm hooking up via DVI to HDMI from my Mac mini. In my struggle to eliminate overscan I managed to set the screen resolution to something not supported by the tv. How do I change the resolution without that screen attached?

Specifically my tv says it's "720p and 1366 x 768 Resolution". The 720p resolution option in OS X made for a ton of overscan (couldn't see menubar or dock at all). So I tried something x 768 and managed to shoot myself in the foot with an unsupported resolution. I thought it was okay to experiment since a resolution change times out if you don't accept it. Apparently that didn't happen for some reason. I've already deleted the com.apple.windowserver.plist in /Library/Preferences as I saw suggested in other places, with no effect.