MacBook :: Password Lost - How To Reset

I have brought Macbook A1181 from ebay it works fine but there were two accounts but I don't know the password and when I try to get back to the ebay seller he is closed he is account. Also I have read the Mac website that I need to use the Code: If you don't remember the password and automatic login is turned off, you can reset the administrator password using the Mac OS X User Install disc. Because a user with the Mac OS X install disc can gain unrestricted access to your computer, you should keep the disc in a safe place. To reset the administrator password using the Mac OS X disc:

1. Insert the Mac OS X Install disc and restart the computer.
2. When you hear the startup tone, hold down the C key until you see the spinning gear.
3. When the Installer appears, choose Utilities > Reset Password.
4. Follow the onscreen instructions to change the password.
5. Quit the Installer and restart your computer while holding down the mouse button to eject the disc.
But didn't received any CDs from him so I don't know what version of CD I need it also I am new to macbook so its fully confusing please somebody help me how to reset my password.