I'm using UltraMon with my dual screens, it will at least be able to restore your wallpaper and icon positions. Works fine for me with fullscreen apps, but both of my monitors are the same resolution, and i can run fullscreen apps at the native resolution too. It also has a quick way to disable the secondary monitor from the system tray if you prefer turning it off completely.
Runs on command line too, so your game shortcut could link to a batch file containing something like this to automatically toggle the second display when you launch your game:
code:
@ECHO OFF
"c:\program files\ultramon\ultramon.exe" /d
"c:\program files\game\game.exe"
"c:\program files\ultramon\ultramon.exe" /e