As has been commented: https://en.wikipedia.org/wiki/Windows_3.1x "Windows 3.1 dropped real mode support and required a minimum of a 286 PC with 1 MB of RAM to run. ... Some older features were removed, like CGA graphics support (although Windows 3.0's CGA driver still worked on 3.1) and compatibility with real mode Windows 2.x applications." So on my Heath/Zenith Z-100 with 8088 and Z80 alternate processors, Win 3.1 would not run. But Win 1.X and 2.X may in principle work. In practice, deciphering the hardware support might be difficult. In the Z-100 world, various hardware products (Gemini) improved IBM PC compatibility, those may be helpful. They won't add a 286 (generally). In the S-100 world, there were a number of 80286 or 80288 CPU boards. I myself have (and exhibited at VCF-E 8.0) a Compupro "8/16" system chassis which replaced the Compupro 88/85 (dual 8088 8085 CPU) with a Macrotech MI-286 (80286 and Z80 CPU). It ran all Compupro software without modification. That's CP/M 80, CP/M 86, and MS-DOS. The Z-100 also runs these as Zenith products. So THAT Macrotech system would in principle be a Windows 3.1 candidate. if it had a video card comparable to IBM CGA (possible). If the I/O structure was compatible. If interrupts can be handled in the IBM PC style. If, if, if...... Win 3.1 is not a priority for me, for reasons I don't see much point in discussing. I can understand interests in it, by the next (after me) generation of vintage computer enthusiasts. 'Nuff said, but I might add there's no particular hardware "target" for Win 3.1, as any legacy "100% PC AT compatible" will do (and emulators). That does not enthuse me, as a HARDWARE vintage computing supporter. herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net