I've been trying to play the very first 3D platrformer ever created called Continuum AKA Alpha Waves. Only for DOS so my Win7 can't run it. So I run it through dosbox. Turns out that I can't control anything. It just keeps going to the demo mode. Any suggestions?

Have you tried running DosBox in Admin mode? Some things don't like taking inputs unless they're being run in Admin mode.