Which "settings" do you wish to reset? Are you trying to re-install the operating system software from the Restore disk? If so, you need to restart the iMac from that Restore disk by selecting it as the Startup Disk with the Startup Disk Control Panel. As an alternative method, you can turn on the computer with the CD inserted in the optical drive and immediately hold down the "C" key until the computer has booted from the Restore disk. Once you have booted from the optical drive, you will be able to erase/reformat the hard drive (if desired) and re-install the OS software from the disk. If you have more questions about your G3 iMac, I'd recommend that you post them in the designated "iMac Forum" for older models with a PowerPC processor. You'll get informative responses from other users who have a lot of experience with your model iMac.