All three preview builds of Windows 8 -- Developer, Consumer and Release -- will expire in less than a month.
Consumers and developers still running preview versions of Windows 8 will need to upgrade soon if they wish to keep using the blocky modern platform, as they're scheduled to expire next month. Those who insist in using the preview builds after the expiration date will see their computer rebooted every two hours, similar to the way Microsoft handles unactivated copies of other Windows releases.
The Windows 8 Developer Preview (build 8102) will officially expire on January 15, 2013. It was first introduced on September 13, 2011 during Microsoft's BUILD conference, and included SDKs and developer tools for creating apps specifically for the new Modern UI interface. Microsoft said it saw around 535,000 downloads of the preview build within the first 12 hours of availability.
The Windows 8 Consumer Preview (build 8250), set to expire January 15 2013 at 6:59 PM, was released on February 29, and revealed to the public that yes, Microsoft indeed ripped out the Start menu. Former Windows boss Steven Sinofsky even said that more than 100,00 changes had been made to the OS since it was introduced to developers months prior. Microsoft claimed that this build was downloaded over a million times in just 24 hours.
Following the Consumer Preview was the Windows 8 Release Preview (build 8400) on May 31, 2012. Also set to expire on January 15, 2013, this version was a bit more refined and included demo apps like Sports, Travel and News. It offered improved multi-monitor support, new Family Safety features, and a "power-optimized" Adobe Flash Player for Internet Explorer 10.
Windows 8 finally arrived in the hands of consumers on October 26, 2012. Consumers who purchase a new Windows 7 desktop of laptop between June 2, 2012 and January 31, 2013 will be able to upgrade for a mere $14.95. Customers who purchased a Windows-based machine prior to June 2 can still upgrade on the cheap until the January 31 deadline, paying $39.99 for Windows 8 Pro.
That said, there's really no reason why anyone should be still using the Consumer and Release Previews at this point given the cheap upgrade prices. Maybe that two-hour rebooting will eventually push stubborn beta users into forking out cash before time runs out on the discount.