Well, Mavericks, fine. But I'm able to run Windows 8 on my old as hell Toshiba laptop, and it's blazing fast. I have completely regained my respect for Microsoft's engineers after Windows 8. They've proven, time and time again, that with the right management, they're able to produce stunning work.
According to Microsoft, you need a CPU with NX, which weren’t around until 2005, and you’d need a at least Pentium 4 (Prescott). Other system requirements are 1Ghz clock rate and 2GB RAM.
Windows 8 runs fine on a ThinkPad X41 Tablet from 2005. That's not 10 years, but it's pretty close. It has a Pentium M and 512 MiB of RAM. The only real issue is that you need to use the generic Microsoft video driver, which isn't quite acceptable for the video playback performance we're used to today (though it does support Aero). For all the other basics, it works great.
