I was reading what someone named "ADRz" wrote ***here on the technet forums***
To be certain WinRT e/devolved from Win32, but programs written to Win32 are not compatible with programs to WinRT. Thus, if you develop a "Metro/WinRT program", it will run on Win8 (but not in the desktop mode of Win8), it would run in Windows RT (what is running in the ARM-based tablets), but it will not run in Win7 or any other previous version of Windows. In its core, Win8 is incompatible with previous Windows versions (thus, the desktop mode).
What he says makes it sound like the WinRT under Win8 is a completely different operating system than previous versions of Windows --> Programs made for Windows 8 won't run on earlier versions of Windows. So does this mean that games made for Windows 7 and earlier are incompatible with Windows 8? Or would Windows 8 use some form of emulation for games and other programs made for older versions of Windows?