Well, Macs weren’t the first. Intel tried to realease a 64bit processor, but it wasn’t a hybrid so it was too (2)advanced for its day (like the Sega Dreamcast) and died. AMD is taking over with 2 hybrid processors (codenamed project hammer. Jackhammer and sledgehammer) and another to be realeased later which is 64bit only.
A 64-bit version of windows have been out for a while. As your ordinary home user/consumer, you’re not seeing it in your corner computer store, but its out there.
If you’ve installed the patch for the blaster worm, you’ve probably even noticed the 64-bit OS options when specifing your operating system for download.