My friend bought an old iMac at a garage sale. It's locked, no start up discs. The people he bought it from have moved already. We don't know where. How can we get into the computer without the usernames and passwords?
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 (source). 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
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 here
You would then mount the file system as writable with
then find out what the accounts on the system are with
then change their passwords with
reboot and get back into graphical mode with
Then check the accounts to work out which one is the admin account.
You should choose one of these options mentioned here: