OSX - Reset Mac OS X 10.5 (Leopard) and 10.6 (Snow Leopard) password without an installer

 Solutions:

1. Power on or restart your Mac.
2. Hold down Command+S on your keyboard to enter single-user mode.
3. This step is optional, checks the consistency of the hard disk before moving on. At the prompt, type #fsck -fy and press Enter/Return. Wait for the checks to complete before going to the next step.
4. Type #mount -uw / and press Enter.
5. Type launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist and press Enter.
6. Type ls /Users and press Enter. This lists all of the usernames on the computer – helpful if you don’t know or remember what these are.
7. Type dscl . -passwd /Users/<username> <password> and replace “username” with one of the users displayed in the previous step. Replace “password” with a new password of your choice. Press Enter.
8. Type reboot and press Enter.

 Source: https://www.it-support-singapore.com/mac-support-articles/how-to-reset-your-mac-os-x-10-5-leopard-and-10-6-snow-leopard-password-without-an-installer-disc/