Chosen Solution
Everytime I place a CD or DVD into the IMAC G4 DVD Drive it states Supported Disc Not Available.
Go to finder>applications>utilities>disk utility Then select HD and Click “Repair Disk Permissions”
The laser is probably dead. It happens to older optical drives some times.
The CD/DVD Drives in these machines seem to be prone to failure, so the unit will need replacing. Out of 6 machines I recently came across, 3 had failed optical drives.