Register/Log-In Pop-Up Box

[drumsy]

We've recently switched our forums over to require registration/logging in to view the forums. What I'm interested in doing is have a pop-up box come up for new members that just allows a user to input a username and password, then click ok, which directs them to a full registration page.

Current members need only to input their username/password and get directed to the forums.

I would like this in a small pop-up if possible.

Any ideas?