With “Tiger” Mac OS X 10.4.7 – there are several ways to get around a lost admin password on Mac OS X.
One way since you have physical access to the system – and I’m assuming you have the Mac OS X install CD disk – is to put the install disk in and restart as if you were going to reinstall the OS. <b>But don’t reinstall!</b> Just go far enough in the install process to get to the “reset password” utility. From there, you can create a password that you’ll remember.
You can also do some “sudo” tricks in the terminal or go into single mode user to reset the password, but if you’re not comfortable with the Unix geek part of Mac OS X, you’d be better off using the install disk trick.