Lowell:

1. Is the mic you are using an electrette type mic?

In my experience, soundcards expect such a mic and have around 5 volts on
the tip of the mic jack.
Electrette mics have a very smalll output, and require that 5v or so to
polarize the element.

You could also have a terrible impedance missmatch.  I would pick up one of
the cheap computer headset mics from radioshack.  Last one I bought was
around $4.00.  Give that a try, then let us know what happens.

73