OK a few questions...

Was the isa card installed when you loaded windows 2000?
if so...
Was the 2k load a clean install or an upgrade?

Does the sound card appear in the multimedia properties in control panel? What else appears in the drop down boxes for play and record? Is the box checked - use only preferred device?

Boot to safe mode - go into device manager - click view, show hidden devices. Apart from the sb16 what other audio related stuff is installed?

What resources is the sb16 using? IRQ, Memory address, Dma channel? What else is using these resources? (click view, by connection, irq)