Sharon,
Thanks very much for your reply.
However, I don't see a Menu option when I open the Volume Control window.
Where exactly is that menu?
Open Volume Controls (start> run> accessories> entertainment> volume
controls.) Click on Options> Properties. You may or may not find Modem
here.
When using my Creative sound card, I had an option for modem here and used
it.
Now using motherboard's onboard sound (nVidia nForce audio). Either
nVidia's mixer does include that option or it's not appearing because this
new system does not an analog modem installed.
If unable to find it here, you should be able to find the same volume
slider/mute box in the modem's properties (control panel> phones and
modems).
Some ISP software includes an additional modem sound control. AOL for
example has a control in their "expert setup" screens.