DOSBox proved to be very good in playing old demos, which don't work on today's machines or operating systems anymore. On the official DOSBox website, there's only a compatibility list for games - PAiN brings you the official compatibility list for demos.
You can add demos that proved to run well on DOSBox on your own.

http://pain.scene.org/services/dosbox/

references:
- What's PAiN? http://pain.scene.org
- What are demos? http://www.digitalekultur.org/en/demos.html