If you deleted the email and didn't write your key down, you may not be
hosed. Some of us got TWO product keys with one registration, so you may be
able to simply sign in at the Vista Beta site and go through that process
again to get your second product key . . . which you should then have
tattooed on your left forearm.
If that doesn't work, you'll need to use another email address and try to go
through the registration process again with a different "identity."