Bass Pro Shops Trophy Hunter 2007 - Can't run setup

[_Antithesis_]

(Game link: http://legendsworld.net/shooter/game/20254 )

To put it simply, I mount the iso, click the setup.msi file within, and get the following message:

"This installation package could not be opened. Contact the application vendor to verify that this is a valid Windows Installer package."

I'm running Windows 7 Ultimate 64-bit, so it isn't like the setup file should have any trouble with the OS. It isn't some 16-bit file that has compatibility issues with a 64-bit OS or anything, so I'm not sure what the issue is.