Os 9 Install After Os 10.2


This is a continuation of my question that timed out and was closed.
I was given a G3 tower (300mhz) with OS 10.2 on it but without a copy of OS 9. THe person who gave it to me sent along a CD with OS9.2.1 on it but I could not boot up from the CD. My last reply through this web site thought that it might be because the G3 was from a office set up that was networked (which it was) and the OS9 CD was meant for that scenario.
I was able to use the CD to upgrade a G3 desktop (266mhz) from OS8.1 to 9.2 and so planned to install the desktop hard drive in the extra drive bay of the tower and use that to run my classic programs/files. As the tower had a two-terminal ribbon cable running the DVD drive and the Zip drive, I decided to take the 2-terminal ribbon cable from the desktop and use it to run the original hard drive and the second hard drive. Due to length issues I used the first cable for the original hard drive and the DVD drive and the second cable from the zip drive and the second hard drive. With this set up the computer would not boot up with either hard drive. Disconnecting the DVD drive from the cable also going to the original hard drive permitted the original hard drive to boot up. My question is, how do you add a fourth drive to the tower? Do I need to put both hard drives on the same cable? Is there a cable with 3 connections?
Eventually I would like to put a version of OS9 on the same drive with OS 10.2 but I believe I need to wipe that drive clean and install a version of OS 9 first followed by OS 10.2. Is that the correct way to do it? If so, what is the best/easiest way to wipe the hard drive clean so that I can boot up from an OS 9 CD?
Thanks for your help. (Sorry for the length of this query)