How to install system 9.1 on second drive of a G4 while running OS 10.5.8 on primary drive

Question

I am Using a G4 OS 10.5.8, trying to install system 9.1 on an erased/reformated disk with system 9 drivers option selected. Can't boot with a 9.1 install disk by holding C key on startup.   When booted with sys 10.5.8 attempting to install sys 9 on the reformatted drive yields error "classic functions are no longer supported"  no luck just copying  the software from the install disk, even though the drive shows up as an available startup drive, it never gets a spinning wheel during startup attempts.
Thinking about reinstalling the original powermac G4 software (there are other partitions or drives available) but trying the path of least resistance first.
Totally open to suggestions

Answer 1

Since you are running OS X 10.5 (Leopard) on that machine, unless you used one of the unsupported install methods your G4 has a processor that is 867MHz or faster (that's one of the requirements for Leopard).
Assuming that is the case, you will never be able to boot the machine to OS 9.1, or to any retail OS 9 Install CD.
The first G4 which met the 867MHz requirement was the QuickSilver '02 model (only the mid and upper speed units); all G4 MDD models meet that requirement.
All of the preceding which are OS 9 bootable (the G4 MDD FW800 model is not OS 9 bootable) can use only the model-specific version of OS 9.2.2 which shipped with them as a bootable OS 9.
The QS '02 models used a stand-alone OS 9.2.2 Install CD, labelled Software Install. Installation of OS 9.2.2 using that is straight-forward - boot the machine to the Software Install CD, and install OS 9.2.2 on the second drive.
The MDD models are a bit different. They came with a combination installer disk, one which booted to OS X but which was capable of also installing OS 9.2.2 (Classic, I think it is referred to in the installer's jargon).
Unfortunately, the installer on those disks seems to have a restriction - it will install OS 9 (Classic) only onto a volume which already has OS X installed on it. So, how to get OS 9-only on the second drive? Two ways -
A) Install OS 9 (Classic) onto the main drive, then copy it via drag-and-drop onto the second volume. Once placed there and tested for booting, remove the install of it placed on the original drive. Be sure to copy the folders named System Folder, Applications (Mac OS 9), and Documents; if there is a free-standing folder named Utilities, copy that too (it often is placed into the Applications (Mac OS 9) folder).
Possible issues -
* since the OS X on the original drive is Leopard, a substantly newer version that that on the OEM disk set, the installer on that disk set may balk at doing this.
• aliases will be broken by copying the system and support files to the second drive. This can include an alias to Sherlock in the Apple Menu Items folder in System Folder and perhaps one or more in the Application Support folder in System Folder. Alises can be repaired - do a Get Info on an alias, and the Get Info window will display a button which can be used to reconnect the alias to the appropriate original.
B) Install OS X (the version on the original install CD set) onto the second drive. Then install OS 9 (Classic) onto that drive. Once it has been tested for booting, throw away the OS X system and files from that drive.
Possible issue - deleting OS X can leave behind some invisible files. Unless you are very short on disk space, these should present no problem and can be ignored - OS 9 will not (can not) attempt to use them.