Today is the end of the road for pre-release versions of Windows Vista. Starting tomorrow, after 2-hour sessions, anyone operating a pre-release version of Windows Vista will find the PC automatically rebooting without providing the opportunity to save any data. The ability to log in normally for 2-hour sessions will only be available until August 28, 2007.
Upgrade information is available at the Windows Vista Preview pages. See the Windows Vista Blog for additional information.