Install Linux or *BSD, and then visit this web site:
[link|http://www.gnustep.org/|http://www.gnustep.org/]
Last I checked it wasn't ready for prime time yet, but it may have enough of an OpenStep compliance to work for you.
I remember getting an offer from Next to run OpenStep on my Intel system. I turned them down. Later Apple bought them out, and I don't think it is offered anymore. No more improvements, support for P4 chips, etc.
You could; however, download Darwin instead of Linux or *BSD. :) Get the core of OSX for WINTEL systems. [link|http://developer.apple.com/darwin/|http://developer.apple.com/darwin/]