Fair warning: mamaich's tool is very very beta, and requires you to unlock (essentially jailbreak) your Windows RT tablet to use. Once you do, his tool essentially emulates x86 on ARM and passes Windows API calls to RT to be executed normally, so it's not too heavy on system resources. He's only tested it with a handful of apps right now—most notably some old school Windows games like Heroes of Might and Magic 3 and some utilities like 7Zip and WinRAR, but they work and he's planning a number of improvements to the tool.