Hello,
Welcome to DaniWeb. Please do not hijack other people's threads... your problem is different and unique, and you are welcome to start your own discussion.
Powerbooks require the C button to be held down to boot from the CD-ROM, whereas your iMAC is seeing the CD-ROM in the drive, and defaulting the restart from there.
Re-install the OS. Then, when the computer reboots, hold down the mouse button when you hear the chime-bong-boot tunes. This will eject the CD, allowing the system to boot from the hard drive.
Let us know if this works for you.
Christian
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