Lost iMac Passwords

[harpjw]

I have inherited a iMac G5, that's good. The password has been forgotten and the Admin. password lost, that's bad. I've tried:

Restarting the computer while holding down the command and s keys at the same time.
Typing /sbin/fsck -y. To do a quick check of the hard disk before mounting it.
Typing /sbin/mount -wu / for read/write access, also tried
Typing /sbin/mount -uw / as an alternative
Typing /sbin/SystemStarter" Starting the network services, which is necessary to gain access to NetInfo
Typing, passwd root, to override the existing root password with one of my own. But the system has not allowed me to write.

I've typed, nidump passwd . However the system does not recognize the command.

What can I try?

 

[Hellhammer]

http://support.apple.com/kb/ht1274

You need OS X disc though

 

[harpjw]

http://support.apple.com/kb/ht1274

You need OS X disc though

Have a OS X install disc

 

[Chozo]

There are a few ways to do it. I'm quite surprised actually how easily (if you know what you're doing) you can change admin passwords without knowing them on a Mac is...