Reset a lost Mac OS X password.
Many times every month we get calls from designers or IT managers who need to reset a lost administrative password on Mac workstations.
Apple has provided an easy method to reset a lost password — although you'll need to have a Mac OS X Install CD/DVD to take advantage of it.
We're posting this short illustrated guide to make the process easier next time it comes up.
Bookmark this tip so you have it handy the next time a user forgets their Mac's administrative password.
Step 1: Start up from a Mac OS X Install CD.
This hardest part of this technique may be laying your hands on a Mac OS X Install CD when you need one. Use a version that is close the the version of Mac OS X you have installed.
Hold the C key as the computer starts to boot from the CD.
When the installer starts, choose your language, and you'll proceed to the welcome dialog.
Step 2: Choose Reset Password from the Utilities menu.
Tip: In previous versions of Mac OS X (10.2 and 10.3), you can find the Resent Password option under the Installer menu instead.
Step 3: Select your Mac OS X hard disk volume.
Select the user name of your original administrator account.
Important: Do not select "System Administrator (root)". This is actually a reference to the root user. Do not confuse it with a normal administrator account.
Enter your new password. Click Save.
Step 4: Quit the Reset Password tool, and Restart your Mac.
Once you restart your Mac, you should be able to log in with the newly changed password.
Source: This question comes up all the time. The most recent inspiration to get this tip written up comes from the in-house creative department at Organic to Go. Apple also provides a nice Technote on this topic.