OK, the iMac with the non working disc drive? It's hard drive is showing up on the working one, right?
If that's the case, what you should do is insert the Tiger install disk into the working one, and reboot the working machine using the disk. (Hold down "C" on reboot, if I remember correctly) From there, the installation process will start on the working one. At some point, you are given the option of where Tiger is to installed. The other machines hard drive should show up, and you can install it from there.