Operation: Inner Space

Inner Space is an addictive, fun and easy to learn game. Acclaimed by reviewers, it delivers hot strategic action play on any computer with any Windows version from Windows 3.1 to Windows XP. Visit the Features page for details. Inner Space is the oldest game still sold, supported & played in its original version. It works unmodified on all Windows versions from Windows 3.1 to Windows XP.

Source:

Software Dynamics' website