Edit: As of version 1.2.2 the BridgeItOptions.txt file is now located in the "BridgeIt" folder in your "Documents" folder. Also all the video options can now be changed from the Options menu in the game.
Open the file "BridgeItOptions.txt" and change the settings:
To Set initial screen resolution. Enable one of the possible values below by removing the # sign in front of it:
#-1600
#-1280
#-1024
Enable this option to run BridgeIt in a window as opposed to fullscreen:
#-Windowed
Add these options if you Bridge It is running slowly:
-GlobalTextureResolution=1
-TextureResThreshold=512
Then save the file and start Bridge It. If you delete the file Bridge It settings will be reset to default and the file will be rewritten with these settings.
This bridgeitoptions.txt file is created the first time Bridge It is run so if you are having trouble running the game this file may not exist. Here is a version you can download:
http://www.chroniclogic.com/bridgeit/bridgeitoptions.zip
Unzip and place in your "Documents/bridgeit" folder. If the bridgeit folder does not exist you will need to create it. Make sure to unzip the file.