When you say you set the "root" password, how did you do it? The administrator password you enter at install is NOT the root password, the root password is a different thing and can only be activated through a little fiddling around in the terminal.
If you ARE talking about the password you entered at setup, then that password is for the first user account created, an administrator account ... which should be in your name as you entered it in your personal details.
On the other hand, if you really ARE trying to carry out commands at the terminal as root (and to be honest, if you can't work out what your password is you really shouldn't be mucking around with root priviliges) then the most common method is to use the "sudo" command: enter your short username and user password. Or, you can use the "su" command and enter a root password ONLY if you've set up a root account. I'd suggest you do not try and operate as root unless you're DAMN sure you know what you're doing.
At the login window, use your name and password as you entered them at setup time.
If you're still stuck, let us know precisely:
- What you did; particularly how you 'set root' and what steps you took.
- What you're trying to do (you do NOT need a root account or password to operate Mac OS X. Period. I've been running mine for 17 months, and have installed all kinds of software, with nothing more than an admin account)
- Where you get stuck. At the terminal, or at the login window?