...when the installation window appears go to the menu bar. There is an option somewhere in there to reset your password.
If you've activated your root account I believe this will set both your admin and root passwords to the same thing. If not, you can still use your admin password to reset your root password from the Terminal using the command 'sudo passwd root'. You'll first be asked for your admin password, then the new root password which you must enter twice.
Ah, won't it be nice to get back in there and start having fun again?
just my two cents on the matter, the other way of doing it is to go into netinfo manager, and under users you will see root. One of its properties is password, and its value is the crypted password. Just set the value to nothing, and you can login to root without a password. Then you can set it back