If you're still running a beta version of Windows 7 – basically any build before 7100 – you'll probably want to upgrade to one of the Release Candidates or go back to your previous operating system.
Starting tomorrow July 1, 2009 all beta versions of Windows 7 will start shutting down every two hours – a huge annoyance if you plan on doing anything on your computer that requires an uptime of any time longer than that. Even if you can deal with prematurely ended computer sessions, after August 1, 2009 the beta will expire completely.
If you haven’t done so already, it's time to clean house and either move forward or backward.
We're guessing that if you've been using the beta for this long already, you'd like to continue. While Microsoft doesn’t officially want to its beta testers to upgrade from beta to RC (clean installs or Vista upgrades are what Microsoft prefers), those who can’t be bothered to backup their test machines can jump right to the RC courtesy of a Microsoft-provided workaround.