Actually, it's this one that you should look at:
It use the INNO installer package. On this line, you could add your .bat script:
Then replace some of the information at the top:
with your own instrument's name and details.
For the installer to work in bundling Csound you will need to have Csound installed in the default directory. This installer will give users the option of installing Csound, or using the one that they have installed already. It'll take some trial and error, but it should be pretty easy to get going in the end.