Written by Jeff Browning.

This method tricks the computer into thinking the computer it’s brand new and leads you through the setup again to create a new administrator account.

This guide should take only about five or ten minutes, but there is some music and you have to boot into single-user mode, so if your in a public place with inquisitive people bring headphones and try to be subtle.

If you want to recover the password of any current user on the target computer in cleartext (that means actually viewing the user’s password instead of just resetting it), check out our other guide on cracking Mac OS X passwords.

Requirements

• • Wireless network password (not a must, but helpful if you want internet on a secured network right away)
  • Headphones (if you’re in a public place and don’t want people giving you weird looks)

Procedure

1. Boot into Single-User Mode

Turn on the computer and when you hear the startup chime hold CMD+S. This boots the computer into single-user mode, giving you root access. It is important to note that this can be blocked by a firmware password. If that’s the case, head on over to our other guide on how to get into single-user mode while locked.

2. Mount the Hard Drive

Once single-user mode loads (it looks like a black screen with white text) we need to mount the hard drive. So at the prompt type in:
/sbin/mount -uw /

3. Remove the “Setup has been completed” File

Now that the drive is mounted we can edit the file system. We need to delete a file that tells your computer that you have completed setup. So type in:
rm /var/db/.applesetupdone
This deletes the file “.applesetupdone” in the /var/db/ directory, which the computer checks for on startup to ensure that the computer has been set up.

4. Reboot

Pretty self explanatory. We need the system to reboot so it can check for the file and not find it. Type in:
reboot

5. Watch the Video

Your computer will shut down and reboot. A setup window should pop up asking what language you want your computer to be in. Just like it would when you turn on your computer for the first time. After you select a language, a welcome video plays. This is when you need your headphones, unless there is nobody around, in which case you can enjoy the little music.

6. Continue Setup

Go through the rest of the setup process.

Be sure to select “DO NOT TRANSFER MY DATA”.

Don’t worry, all of your old files will still be on the computer.

At one point during setup you will have to configure your internet connection, this is when you need your wireless password. It’s fine if you don’t have the password, you can enter it later if you need to.

7. Set up the Administrator Account

Near the end of the setup you will be asked to create an administrator account for your computer.

Be sure to make the name of the admin account different from the existing one.

You can name the account anything that you want, except for the name of the old administrator account. If the new account is given the same name as the old one it will overwrite the old account, causing all the account’s files to be deleted. That is not optimal.

8. Finish Setup and Log In

Wrap up the setup and the computer should automatically log you into your new administrator account.