AFAIK the only non x86 versions of Windows were the Windows NT 3.1 to 3.51 (and maybe not all of them) and they were available on MIPS, Alpha (32bit mode only) and (I believe) PowerPC. In any case they are all dead now (have been for a long time, I would say at least 3 years).
NT 4.0 Also support these platforms to SP3/4 + IE4. after this everything but Alpha and X86 was support untill Sp6 and then M$ drop'd support for Alpha with Win2k RC1 I think. A interesting note about Win2k on alpha was that it was fully 64-bit.
Thanks Steven