I've actually been doing a ton of research on this.... there isn't really any way to get OS 4 on a non-amiga, that I can find.. I did find something called Amiga Reaserch Operating System, or "AROS". It's an OS biased on the original Amiga OS, re-built from the ground up by a team of developers. It's open source, so anyone can play around with it and format programs for it. They've made it so it can go on pretty much any computer...
It seems pretty good, but It's currently about 80% complete. I've been trying to get it to work on one of my computers, but I've got no idea how to get it to work on a Windows XP...
But, then again, I don't really know anything about this.
Anyway, back to AOS4, It was originally made for the AmigaOne, a computer made by some company in Europe, I think.. But, anyway, the computer's arn't made anymore and I've not been able to find any current information on Amiga Inc...... And knowing the Amiga's past, It's not really a surprise.