July 1st is the day that the Windows 7 Beta will begin shutting down every two hours. Which is Microsoft's way of telling you to go get the Windows 7 Release Candidate(really, you should have done it quite a while ago).
Just to make sure you don't get to keep Windows 7 Release Candidate for free either, it will begin shutting down every two hours or so about a year from now. Remember, Windows 7 is scheduled for public release on October 22nd.
To your success,
Tim