skype mic vs. pre-amp mic ?

[Eddy]

Can anyone help me out with this mic problem?

I have a computer which is set up specially for audio recording.
Expensive external sound-card, high quality pre-amp microphone:
recording is great.

Then I decide to learn a new language (Greek!) on this computer, using a
teach-yourself CD-Rom. There's a facility within the language-program
to compare my pronunciation with that of the expert on the disc. You
just say the words into your mic. If I use my high-quality microphone,
the system works fine.

However, for regular language-practice I don't want to be connecting up
my expensive pre-amp mic each time, OR leaving it connected continually.
So I bought a simple and inexpensive skype microphone & ear-piece. By
having plugged this (i.e. the pink jack) into an old cassette recorder I
know that it works - the recording quality is pretty good, in fact. But
when I plug this little mic into my Edirol external sound-card, using
the same socket as my big expensive pre-amp, . . . nothing records.

What's up?

Thanks.

Eddy.