I was able to do this ! YAY ! I believe I did something incorrectly on the first go with the PRAM reset. I was able to enter Single User Mode with original disk. Yay ! It was indeed the firmware password! Thank you Kappy !
Following Kappy's steps, I did the following;
If you're running OS 9, you may need another mac (though i suspect a PC with firewire and a HFS driver would do) and a firewire cable. You will need to delete preferences pertaining to keychain access and any keychains in the preferences folder in the system holder The first imacs ran this so its plausible
If you're running OS X on the imac
Single user mode would do the trick unless there's open firmware password protection in place
To go into single user mode
- Press the power button to start the computer.
- Immediately press and hold the Command (Apple) key and one of the following: the "s" key for single-user mode. (Command-S) This should boot into a white screen, and iirc throw you into a command prompt
These instructions should work for older versions such as 10.4. Khafshoh S' version works for newer systems 10.5 and better - 10.7 also has yet another option for resetting the password involving the 'resetpassword' command in lion recovery.
Instructions for changing the password are based off of Apple's documentation though the documentation goes very in-depth.
You would then mount the file system as writable with
mount -uw /
then find out what the accounts on the system are with
ls /Users/
then change their passwords with
passwd username
reboot and get back into graphical mode with
reboot
Then check the accounts to work out which one is the admin account.
