Dear Aunt TUAW,
I recently added a second external monitor to my 13" MacBook Pro. My problem comes with the OS X Lion features that give windows a 3D depth-look, specifically, the shadow effect.
As a window on the external monitor approaches the virtual border of the built-in LCD of the MBP, the shadow extends between monitors, creating a shadow/shade over the windows on the LCD (that is to say, if you park a window to close to the edge, the shadow extends the other display).
Anyway to turn off the shadowed window effect?
Your loving nephew,
Auntie turned to TUAW's braintrust, who quickly pointed her to Unsanity's Shadowkiller haxie. Released in 2006 and "Not compatible with Mac OS X 10.6 Leopard," Auntie can confirm that the haxie works just fine with Lion.
Download the dmg, copy the app to your Applications folder and then launch to kill the window shadows. Launch again to bring them back.
Hugs and a big thanks to everyone who helped find Seth the answer,
Particular thanks to @shabooty, @basraayman, @oboewan, @jtregunna, and @capii