Trying to install classic system on iMac G5

Hello,

I just purchased an old iMac G5 with OS X 10.3.9 and I want to install OS 9.1 classic in order to run old programs.

I have the iMac system software CD and the 4 restore CD. I understand that I am suppose to start the computer

by inserting the install CD and holding the "C" key during startup. I have done this and the computer is not starting

from the CD. After startup when running installer I get the error, "Classic cannot update files in "System Folder" on

iMac Install CD because the disk is read-only. Any suggestions would be appreciated.