Hyper-V Program Manager
I stumbled across the Calmira project a long time ago - and just found out that they are working on a new release. This is a bit of an odd project - but interesting none the less. The basic premise is to bring the Windows XP user experience to a Windows 3.11 environment:
I am not sure why you would really want to do this - but it is interesting to see just how good a job that they manage to do with this. If you want to check it out (and have a copy of Windows 3.11 handy) go to http://www.abzone.be/
I remember using Calmira back in 1997.
As you might gather from the year, Calmira wasn't really intended to bring XP to Windows 3.11, as to bring the Windows 95 program launcher to Windows 3.11. Mixed environments would've been pretty common -- it took a while for 3.x to die out -- and computer novices (plenty of those in 1997!) might not be able to learn Program Manager on their own.
I imagine the XP theming came later. Since the application logic had already been written, changing the program appearance would've been comparatively simple.