A recompiled app that provides you with such a feature is now available
The lack of a Start button in Windows 8 is considered one of the main reasons why people choose to stay away from the new operating system, but several third-party solutions are now available in this regard.A Start button application is now available on Windows RT too, allowing consumers to make their tablets a bit less confusing in case they can’t get used to the new Modern UI.
The ClassicStartMenu app posted on XDA Developers forum is available for Windows RT users who have decided to jailbreak their devices and is based on the popular Classic Shell application compatible with the desktop version of Windows 8.
Keep in mind that this application requires a jailbroken Windows RT tablet and it doesn’t ask for a reboot. In case you restart your device, the jailbreak is completely lost.
Click here to download ClassicStartMenu for Windows RT (the file is delivered as a ZIP package, so a compression tool for Windows RT is needed).
For more information on the Windows RT jailbreak, check out this article.