Even Microsoft (or does Windows XP run on a 68k Amiga? I don't think so).
Microsoft Windows XP does run on most "IBM compatible" machines, not just "one specific model"
You might want to ask Apple why they have chosen to go this way and produce OS X for Apple-branded machines only.
Becouse that way they can put higher price tag on the product. If they had chosen X86 instead of PPC, there would have people asking "Why can't I just install it on cheaper IBM compatible PC?" and eventually there would have been something, like "MacOnLinux" for standard PC's ages ago.
But just lately they have noticed, that they can't get more user/developerbase unless they lower the prices, and they've considered doing X86 version of MacOS X afaik.
