Uh, that's not how it works cause it can rip any audio disc or even games from other systems.
That message is normally followed by a prompt for a title:
"No base filename for the disc was specified at the prompt and the disc could"
"not be identified as a valid PC Engine/TurboGrafx-16 CD-ROM game."
"Enter a filename now:> "
Make sure you open a Command Prompt instance from "Programs" -> "Accessories" and then CD all the way to the folder where you have TurboRip in - don't double click on TurboRip via Explorer to run it.
Also, just in case, make sure you have the
latest version - linky.