How do I tell if I already have the CoreAudio2ASIO driver?

I don’t use a USB audio interface but as I’m experiencing some issues with Nuendo 6.0.7 on my Mac I’m trying all the recommendations.
So, I’m trying to install the CoreAudio2ASIO patch but when I’ve got the installer running and have gone through the user agreement panes, the “install” button is greyed out.

Does this mean I’ve already got it installed?
How can I tell whether it’s already installed on my system?