Do your Sound Blaster 16 ISA sound cards have jumper settings? If so, have you verified that they are each set differently to avoid conflicts? Do they have a PCI jumper setting also (some old ISA's did)? I would check the sound blaster web site for w2k driver updates and instructions (if you haven't already). Also, Microsoft knowledge base has some papers on issues with sound blaster 16 sound cards and windows 2000 that you will want to read before you go any further.
Here is a link to start with:

http://www.creative-asia.com/support/specs/sound/sb16/


Also, you're NOT going to like this:

From: http://asia.creative.com/support/faqs/general/win2k.html#q7


Q7. How are Creative sound cards being supported on Windows 2000?
Windows 2000 comes with default WDM drivers for compatible Creative sound cards listed below:

www.microsoft.com/windows2000/upgrade/compat/search/

This means that Windows 2000 will be able to recognize and perform a silent installation without prompting for new drivers. The default drivers that comes with Windows 2000 will enable only basic audio functions like playing and recording MIDI, WAVE, and CD. These features are accessible through Windows Media Player and Windows Sound Recorder.

Support for ISA sound cards like the Sound Blaster AWE 32 or Sound Blaster AWE 64 will come from Windows 2000 itself. Owners of these sound cards are advised to continue using their current OS or upgrade to a PCI sound card if they wish to upgrade to Windows 2000.

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Good luck! I really hope you get them both working--sometimes it can be done regardless of the recommendations.