Reset a user's password in single user mode

We needed to reset the password on a Leopard system, but we didn't have the OS X install DVD available. 

1. Boot into single user mode (press Command-S at power on)
2. Type fsck -fy
3. Type mount -uw /
4. Type launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist
5. Type dscl . -passwd /Users/username password, replacing username with the targeted user and password with the desired password.
6. Reboot

This allows you to reset the password in single user mode without booting from the install media. 

Change Mac admin password without the disk

Creating a new Admin on Mac Os X: 
Here's how to reset your OS X password without an OS X CD. 
the Working solution for me was to create a new admin 
you can create new admin like this by deleting a specific file. 

You need to enter terminal and create a new admin account: 

1. Reboot 
2. Hold apple key + s key down after you hear the chime. (command + s on newer Macs) 
3. When you get text prompt enter in these terminal commands to create a brand new admin account (hitting return after each line): 

mount -uw / 
rm /var/db/.AppleSetupDone 
shutdown -h now 

4. After rebooting you should have a brand new admin account. When you login as the new admin you can simply delete the old one and your good to go again! 

Apple stores wont reset it for you. Computer shops may charge you $50 to $200 trying to reinstall the Mac and failing at end.


http://en.kioskea.net/forum/affich-73393-change-mac-admin-password-without-the-disk