Everyone and his brother got a free copy of RC1. A subsequent build was
available for download, but it won't do you any real good because the
betas are all time-limited. You'd be wasting your time to install one
after Vista's release date.
MS didn't give out free versions of the RTM to open-beta testers. In
that respect, this beta test was different from XP's. I'm afraid that
you're going to have to get out your credit card if you wan an upgrade
version.
