Help!!!! password help

So I have a 17" Macbook running 10.4.8 and I need make some software updates. The computer was set up by someone who is no longer around. I need to be able to change the password somehow so I can make these critical updates. Please help out as this is my work computer and I need to make these updates.

thanks!

Jon

A search in M-F brings these (and so much more...) :

http://www.mac-forums.com/forums/showthread.php?t=98783&highlight=reset+password

http://www.mac-forums.com/forums/showthread.php?t=96180&highlight=reset+password