Ed Bott offers up some Windows 7 setup secrets, though only two of these qualify as secrets (i.e. are not widely known), and both of those apply only to the RC. Still interested? You should be. As always, Ed has some good info:
Secret #6: Unblock the upgrade path for your Windows 7 beta
The RC blocks upgrades over any build earlier than 7077. If you’ve been running the original beta (Build 7000) and you try to upgrade, you’ll see an error message. But if you insist on doing the upgrade anyway, there’s a workaround.
Secret #7: Unlock extra editions
The ISO image available for download from MSDN, TechNet, and Microsoft’s public download site contains Windows 7 Ultimate edition only. If you’re evaluating the operating system to see how it fits in your home or office, you might want to try another, less expensive edition to see whether its mix of features is acceptable. To unlock those other editions, you need to follow the same procedure as in the previous item ...
Check his post for the details.