Andrew Tait decided to see if an install of Microsoft’s original Windows, could be upgraded through each version to end up at the current version. Its amazing that yes it worked, and that Windows 3 programs continued to work in Windows 7.
Perhaps even more remarkable, is that Windows 1 was deigned to run on an 8086 processor, clocked at 4.77MHz with 256k of RAM. Using VM Ware it can still be run on modern hardware.
A parting thought…The entire Windows 1 OS will fit in the L2 cache of any modern processor.