With latest systems, it comes more and more complicated to get a running DOS-system. An alternative are emulators. There are two DOS emulators. Both can run a couple of old Games and Demos, it's worth trying out both.

DOSEMU (Linux/x86)

DOSEMU is no real emulator, as it doesn't emulate the CPU instructions, it only gives you a way to run a real DOS in a Linux System. As it runs CPU instructions directly, it only works on x86 CPUs.
DOSEMU Homepage

DOSBox (Linux, Windows, MacOS, others)

DOSBox is a real emulator, thus running on a couple of platforms and probably the better choice for the future.
DOSbox Homepage

ScummVM (Linux, Windows, MacOS, others)

If you are playing old LucasArts Games, there's a better alternative than using DOS emulators: ScummVM implements the engine of the well known games like Maniac Mansion, Zak McKracken or Monkey Island.
ScummVM Homepage