In teaching an undergraduate course in Operating Systems, it is instructive if the students have an actual operating system they can study and modify. Care should be taken, however, in selecting a system that the students can realistically be expected to understand. Xinu/WU retains the advantages of its parent PC-Xinu [Fossum 1987]; a small yet relatively complete operating system for the IBM PC, supplied with full source code and able to run within its development environment. Xinu/WU incorporates three particular enhancements: an improved implementation, integration into Borland International's Turbo C™ run-time environment, and more effective use of the windowing system. The conclusion is that Xinu/WU increases the possibility of using such a system in an undergraduate Operating Systems course. Two ways in which it can be utilized are presented.