Samuel A. Falvo II's _(Dolphin | http://sourceforge.net/projects/dolphin) is an *(OS) for PC and compatibles; the project has been going for some time and has undergone several conceptual changes. Samuel has adopted a virtual machine scheme, where only a _(VM) runs in ring 0 and all the rest of the system is implemented as ring 3 shared libraries (much like _(AmigaOS)). These libraries use _(VM) calls in order to access the underlying hardware. There is actual code floating around for this project, such as a bootsector that you can tune to boot your own protected mode _(OS). There seems to be actual progress this summer. Check all of that out from their homepage.