Turn x86 Windows into RT?

I have a question which may sound weird: Is it possible to turn the "full" Windows 8.1 into Windows RT?

The reason I am asking is because some of my relatives keep bringing me their laptops every month or so because "it has over 400 viruses and is very slow". The culprit of course are a load of "Registry cleaners", TuneUp Utilities and other scareware + a dozen toolbars and trials for online backup services.

Sure I can just reinstall Windows but it doesn't really solve the problem. They don't know how they installed these things and neither are they able to distinguish between legitimate and shady software - and I can't really blame them for that. Even for geeks it's very difficult nowadays to avoid crapware.

So what I am thinking about is reinstalling Windows 8 on the laptop and then somehow "lock it down" so it will only run built-in desktop apps and all apps from the Windows Store just like Windows RT.

Any ideas how I could achieve that?