Although this pre-release version of Windows 7, it is available for download until August 20, 2009. After that, you can still install the RC and you can get a product key if you need one, but will NOT be able to download the software.
Once installed on your PC, the RC will expire on June 1, 2010, however starting on March 1, 2010, your PC will begin shutting down every two hours. Windows will notify you two weeks before the bi-hourly shutdowns start. To avoid interruption, you’ll need to install a non-expired version of Windows before March 1, 2010. (Learn more about installing Windows)