Runing Windows 8

First of all, it's worth noting that the finished version of Windows 8 is still only for x86/64 PCs; there isn't a version of the specially-made Windows RT for ARM devices that you can download and install on existing devices. It's only available on released tablets such as Microsoft Surface RT.

The vast majority of apps in the Windows Store will run on both. Microsoft has even confirmed it will offer Flash functionality for IE on Windows RT (at least on what it calls the "initial delivery of Windows RT PCs").

Windows 8 doesn't include the desktop Office apps that will be bundled with Windows RT either and of course it runs all the x86 desktop apps that won't work on RT. It also has the optional Windows Media Center.