A hacker claims to have found a method of bypassing the code integrity mechanism in Windows RT, therefore allowing for desktop-style programs to be installed on the platform. From Computerworld:

The hacker, who uses the online moniker "clrokr", documented the bypass method in a blog post on Sunday.

Windows RT is a special version of Microsoft Windows designed for lightweight PCs and tablets that are based on the ARM architecture, including Microsoft's Surface tablet. Compared to Windows 8, Windows RT only allows Metro apps downloaded from the Windows Store to be installed. These applications are designed only for the Metro interface and don't have access to the regular Windows desktop.

Hacker finds way to run desktop applications on Windows RT