Resetting administrator password on a Mac

Assuming you have forgotten your administrator password, the most common way to reset is with the help of the Mac OS X Installation disc.

To reset the administrator password using the Mac OS X Installation disc:
1) Insert the disc into the computer, and double-click the Install Mac OS X icon.
2) In the Installer, click Utilities, and then click Restart
3) When the Language Chooser appears, select your language, and then click the Continue button (looks like an arrow)
4) In the Installer, choose Utilities > Reset Password
5) Follow the onscreen instructions to change the password.
6) Once you reboot and log back in, be sure to change the password for your login keychain to match your new account password so your keychain is unlocked when you log in.

If you don't have the Mac OS X Installation disc handy, you can use these steps instead:

1. Restart in Single User mode (hold Command-S during startup). Note that single-user mode always uses the US English keyboard layout.
2. At the prompt, type this followed by Return: mount -uw /
3. Type launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist and press Return.

4. Type ls /Users and then press Return.
5. Look at the listing and note the short name (username) of the affected user account.
6. Type dscl . -delete /Users/username AuthenticationAuthority and press Return.

Note: Replace "username" with the affected user account's short name you noted above.

7. Type passwd username followed by Return.

Note: Replace "username" with the affected user account's short name you noted above.
8. At the "New password:" prompt, type the user's password, then Return. Note: It is recommended that the original user's password be used to match the keychain password.
9. At the "Retype new password" prompt, type the same password, followed by Return.
10. Type reboot followed by Return.