The Raspberry Pi Foundation has spun Debian i386 with PIXEL for PC and Mac systems. This should run on on old x86 systems with at least 512MB of RAM. They are doing this x86 effort to try to make it easy for schools to run on their PCs so they have the same environment on x86 and ARM and for wider-spread testing of their desktop environment.
This Debian+PIXEL i386 system is now available for testing in prototype form. Those wanting to learn more about it can read this RaspberryPi.org blog post.