Help with downloading SO mod

[T23]

I have attempted to install special ops mod several times, but I keep failing. Each time I install it, and then try to open the game, I get the following message: "The program was not installed using the provided installer."

I followed install directions that I got online. They went something like this.

1. Inside the DFX folder, make a new folder, naming it "whatever"
2. Copy and paste entire contents of DFX folder into new folder.
3. download SO mod into the new folder and open it to that folder.
4. run/install.

Each time I do this, everything seems fine (i even get message that the mod was successfully installed). But, I cannot open and play the game.

Anyone able to help me with this?/?????