This article is from the GNU Chess and XBoard FAQ, by Tim Mann firstname.lastname@example.org with numerous contributions by others.
WinBoard does not run on Windows 3.1 or Windows for Workgroups 3.11, not
even with the Win32s compatibility package. The main problem is that
Win32s does not have threads or real concurrent processes. A port of
WinBoard to Windows 3.1 is possible in theory, but it would be difficult
and messy, and no one is going to do it.
WinBoard runs well on both Windows 95 and Windows NT.