Many old Demos/Intros support the GUS (Gravis Ultra Sound). There is a tool that can emulate the GUS in a DOS-Box under Windows.
GUSEmu Homepage


VDMSound is a tool that emulates a SoundBlaster for the DOS-Box in Windows NT/2000. It's released under the GPL, so you can also get the source!
VDMSound Homepage

SoundFX 2000 from Softsystems is a tool similar to VDMSound, but it's a limited Shareware that works only 3 minutes for each program.
Softsystems Homepage