I was recently asked to re-install OS X on an older iMac G5.
Problem was that the owner had lost the recovery disks.
He had a mate that lent him the recovery disks to a slightly later model of iMac… but he couldn’t get it to work.
I had a quick go, but booting from the recovery disk gave the error:
OS-X cannot be installed on this computer
I decide to check the net, and I find out that you need to use the exact same version of recovery disks that you get with the computer.
It seems like recovery disks are computer type specific.
The moral of the story is: if you own a Mac computer, don’t lose the recovery disks, otherwise fixing some problems can become very difficult… or you can try installing yellow dog linux!