If for some reason you're still running Windows 7 Release Candidate (build 7100), today is the day that you'll to see bi-hourly shutdowns. The RC was released in May 2009 as a final public test before Microsoft finalized the Windows 7 RTM build in July 2009.
While Windows 7 RC has been free to use without restrictions since its release, Microsoft made it no secret that March 1 would be the last day that users could continue the free ride. Users who haven't heeded the regular pop-up warnings of the RC's expiration, encouraging backup of data in preparation of migration to another version of Windows, will now experience a shutdown every two hours.
Those who continue to work through the shutdowns every two hours will see on June 1 a shift to a "non-genuine experience," which replaces the backdrop wallpaper with the message "This copy of Windows is not genuine" plastered at the lower right corner of the desktop.
Anyone out there still with a now-narcoleptic Windows 7 RC machine still kicking around?