How do I install AmigaOS 4.1 on a standard x86 system?

You can't AmigaOS requires PowerPC processors

A PowerPC microprocessor is required for the most recent release, AmigaOS 4.

Supported hardware

I know this question is over 2 years old, but have you taken a look at AROS? AROS is an Amiga-like OS that runs natively on x86 hardware. There's a distro of AROS called Icaros Desktop which is frequently updated, and works on both bare metal hardware and in a VM.