I think you're out of luck
To use classic, Mac OS X needs not only a System 9.1 folder, but to modify it during install. You only easy recourse is to use the system 9 that came with your iMac, upgrade it to 9.1 if it is 9.04, and install OSX overtop.
Some of the gurus on these forums may know a way to boot from your install cd, install 9.1, and perhaps find a way to get an already installed OSX to add classic support. I doubt that that will work, however.
p.s. - how did you convince anybody to take back software you've used???
Closed Captioning of this post is brought to you by your arse, in thanks for using cushiony soft tissue.