Unable to enter my license code

Greetings!

I've just gotten back from GenCon, and I'm trying to use my spiffy new d20Pro. So I downloaded the XP version and installed it. When I run it, I get the start up dialog, and I press "Register". That takes me to the registration dialog, where it asks for:

username:
password:
confirm:
email:
confirm:

I was given a user name (first name, space, last name), which I've tried in mixed case and all upper case. I also know my email address, which I tried in lower case and upper case. The only other piece of information that I have written on my receipt is my license number...which I tried as my password.

Obviously, none of this worked, thus my visit here. When I entered these in, I was given an option of purchasing licenses, but no option for entering a license.

What should I be doing?

-Thomas