os 9 installation on old imac problems!

Just got an old blue imac from a guy I work with, and an trying
to re-install os 9, as he had installed ubuntu on it. I have the retail os 9 cd,
and when i hold the "c" button on start-up, it just goes into the ubuntu boot strap menu, giving me options to boot ubuntu, or boot Cd. when i boot cd, it thinks for a bit, then goes back to the menu. sometimes it will show a little folder with the mac face on it, which switches to a question mark and back. what should i do!
Thanks

Your just going to go around and around,boot,ubuntu,macface, Over and over
...I would take out the drive,put it in another Mac or a PC and nuke the drive,
then put it back in the imac and reformat with drive set up on the mac os dics
REMEMBER..... Imacs need firmwear and with out the Imac install dics that
came with your machine,you will have to download the correct firmwear and install it on the Imac before the OS dics.

will do-
on installing firmware, can i do that from a non os 9 computer?
(never worked with os 9 before... have a macbook which i know the ins and outs of but this thing i'm stuck with! ^_^ )

I use an old pc to nuke ide drives in then return it to the host machine. You can download the Imac firmware on a Mac or PC, burn it to a disc, With the hard drive back in the Imac use the OS9 dics to reformat the drive with Drive set up,its in a folder on the install window.. Now... you can install OS9 next BUT,as soon as its installed after restart put in the firmwear disc you made and follow the instructions as you may have to press the programers key next to the usb jacks on the side of the imac or load the firmwear first as its self extracting and then the OS9 install disc. Dont goof around as all the firmwear is not in OS9 and the machine will go dark and may not restart for a day or so. Oh ya you hold down the C key to boot from the OS9 disc on the clean HD. You have to use a paper clip to push the programers button,theres a circle logo with a swish over the hole.