Ever since the first major update to Windows 8 was announced, there have been reports of people unable to install the update in both the regular version of Windows 8, and in Windows RT 8.0. If you remember, Microsoft inexplicably had the 8.1 update available through the Microsoft Store, rather than through the regular update mechanism built into the operating system.
To deal with these nagging problems, Microsoft has unveiled a pilot program in select markets with the intent to solve users' updating issues. If you have this recurring problem, check Windows Update in your Control Panel. The update may go through for you now.
There is also a manual method of installing the update if you are running a tablet with Windows RT, which you can find at this link. In order for the update to install, you must first have Update 2871389 already installed in your system, and this holds true for either Windows 8 or Windows RT.
You can read more on this solution at Paul Thurrott's Supersite for Windows.
