The game is hard-coded to run at a resolution of 800x600 . On modern high-resolution monitors, it is often best to manually set your desktop resolution to 800x600 before launching to avoid scaling issues. Master of Orion 3 on Steam

The 2003 release is well-known for having bugs and unfinished features. Longtime players strongly suggest using community resources to improve the experience:

To download Master of Orion III (2003) legally, you can find it on major digital storefronts as a standalone purchase or as part of a series collection. Official Digital Retailers

A primary fan site for fixes and great patches that make the game more playable.