If you have access to MSDN or TechNet Plus, you will be able to start downloading the Windows 7 RC from the 30th April, using your subscriber site.
From 5th May everyone will be able to download via the customer preview program. As with the Beta, the Windows 7 RC Customer Preview Program is a broad public program that offers the RC free to anyone who wants to download it. It will be available at least through June 30, 2009, with no limits on the number of downloads or product keys available.
Heads up! The Windows 7 Beta will expire on August 1, 2009 so be prepared to rebuild your PC with either the Release Candidate (RC) or another valid version of Windows before July 1, 2009. You will receive a warning two weeks prior to July 1; after this date, the PC will begin shutting down every two hours.