pass help?

i've had my computer for just over a year and i've never changed the password. but when i try to update and it asks for my password, the original pass doesn't work.
caps isnt on and i dont know what to do
i heard there was a way to change your password on terminal, but i dont know the command.
any help please?

Do you have the OSX install disks????

yeah.

Here ya go:

Change Admin Password using OS X Install Disks