the entire aztec ftp site with drivers for all isa soundcards is archived on vogonsdrivers.com; however, if i remember correctly win98se ships with wdm drivers for the azt2320 that automatically install straight out of the box. if you go this route the windows kernel handles all the sb pro emulation in the command prompt virtual machine. wavetable midi (using the roland licensed soundbank) is also provided at address 330. in fact, i think the yamaha opl3 that's onboard the azt2320 is unavailable with the wdm drivers.
i wish i could remember the details better, but i spent so little time playing with the wdm drivers before switching to vxd. the azt2320 is an excellent windows soundcard (and now dos too with unisound). it is perhaps the quietest isa card i have ever used plus it has a real licensed yamaha opl3. only my ess es688 with a ymf262 is favored more (probably because it's non-pnp, but even the azt2320 has wss support while the ess does not).
vxd drivers will install a specific entry in windows device manager that handles the sb pro + adlib/fm configurable addresses in a command prompt virtual machine. there will also be a separate entry for the mpu401 port. the wavetable midi emulation using the roland soundbank will be unavailable, replaced by the hardware mpu401.