Hihi
The 8MHz ARM2 in the Acorn Archimedes A3000 was capable of running PC software at a speed that wasn't too bad, albeit 8086 only
This is because the emulation was done in assembly, most modern DOS emulators are written in C, hence they suck.
There's no reason at all why a reasonably fast 8086 emulator couldn't be written (66MHz ARM9 is much faster than an 8MHz ARM2), perhaps even a 286 or 386 emulator (although things get very hairy with the 386 and you'd have the MMU problem to contend with too)
So I suppose the short answer is no to windows, possibly yes to DOS games, I certainly don't think such as pinball fantasies are out of the question
I'd estimate even with a really efficient assembly core you'd be looking at 8-16MHz 386 type performance though, you wouldn't be running quake on it, put it that way