Classic Windows games
At the end of the DOS era, PCs started to mount the latest Operative Systems from Microsoft. Starting from version 3.1, Windows became very popular and more and more software houses began to produce games for Windows.
The first games for Windows 3.1 weren't very popular; there were solitaire card games, puzzle games and little else. With the release of Windows 95, 98 and Windows XP, the Microsoft OS became central in the development of mainstream video games like Age of Empires and the Civilization series.
Unfortunately, backward compatibility quickly became a problem: it's easier to run DOS games using an emulator. The only safe way to play old Windows games on recent PCs is to install them directly on an older version of Windows or, if you're an expert, use a Virtual Machine.