It has only been a few days since Microsoft officially released MS-DOS 4 as open-source, and people are already finding new and inventive ways to put the operating system to use. However, you can’t really beat going back in time and putting the operating system on the exact same hardware that it would have ran on back in the day. This is what someone has achieved with an IBM PS/2 by building MS-DOS 4…on MS-DOS 4.