DOSBox

DOSBox is an emulator that allows you to emulate an Intel x86 machine with sound, graphics, mouse support, ...
In short, it will allow you to run most DOS games on any PC.

Indeed, old games designed for DOS no longer work under Windows XP, Vista, and later versions of Windows. Another limitation is the hardware of the computer. Indeed, these old games are not compatible with the new motherboards, sound cards, ... (which makes sense). To overcome this problem, DOSBox emulates everything you need (sound card, graphics card, ...) to allow older games to run correctly.

Useful links :

• Official Wiki (FAQ)
• List of compatible games (including : Command & Conquer: Red Alert)

Note : DOSBox also allows you to run old DOS programs. Although DOSBox is especially designed to be able to play old DOS games turning.