Currently Being ModeratedMay 3, 2012 1:50 PM (in response to tangopenguin)
As soon as you turn the computer on, hold down C on your keyboard and it should boot from the CD. If that doesn't work, you can hold down option until the boot menu comes up and choose the CD from the list. The second option always worked best for me with my G3.
Currently Being ModeratedMay 3, 2012 3:08 PM (in response to tangopenguin)
Is the Panther disk from which you're attempting to boot your iMac a retail/universal installer version (black disk with a large silver X on it), or is it a grey Restore disk for another model Mac? If the latter is the case, you can expect problems booting from it, even though it will mount on the desktop and its contents can be read. Hopefully, your iMac's firmware has been updated to version 4.1.9 - maybe prior to the Jaguar installation.