This might work,
Type MSD from the DOS prompt to view your IRQs, DMAs etc.. MSD is not a perfect program and sometimes doesn't give you the whole story but it comes with DOS 6.22 so go ahead and use it.
Install the DOS software for your onboard card so the settings will be listed in your Autoexec.bat and Config.sys.
Then set your IRQs, DMAs etc. to something other than what the onboard sound card is using.
Look here for the jumper settings for your Sound Blaster 16. Double click the picture of your card to see a bigger view of it.
http://asia.creative.com/support/specs/sound/sb16/
Then type REM in front of all the lines for your Onboard sound in the Autoexec.bat and Config.sys.
Install the software for your SB 16. You shouldn't need anything other than SBBASIC.exe
To edit or just view your Autoexec.bat and config.sys;
type;
EDIT autoexec.bat
EDIT config.sys
from C: prompt
Post back here with the scoop