XDA developer mamaich's new utility allows you to run full x86 Windows applications on ARM based Windows RT tablets.
The tool which is currently in beta, requires you to unlock / jailbreak your Windows RT tablet. Once you do, his tool 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 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.
The developer has a list of apps and games he plans to support in the next few releases.
Forum thread: Running x86 apps on WinRT devices (beta version)
Source: Lifehacker