Can anyone think of things that do run an operating system that will definitely not run on Linux?
I have seen cell phones, PDAs, and even parking meters that run some version of embedded Linux.
Bill Gates' house will probably never run Linux.
Linux uses the Intel 80386 chip's protected mode-functions extensively, and is a true 32-bit operating system. CPUs before the 80386 will not run post-2.4 Linux kernels as these CPUs lack protected modes.