Media Center m7457c Question regarding audio input

On the front of the tower for the HP m7457c Media Center, there are
the standard jacks for headphone, microphone, and USB plugs. There
are also four additional jacks for audio and video. They are:
1. an S-Video input jack
2. a Composite Video input jack
3. a pair of RCA jacks for audio input (red & white for right and
left)

My question...How do you get these jacks to be active? That is, I
plugged the output cables from a separate VCR into the RCA audio and
composite video jacks to get the images and sound onto the PC and
nothing happened!!

There is no problem with any of the jacks on the back of the
tower...only the ones on the front present this problem.

Can anyone help or advise on next steps? The folks at the HP tech
line are helpless!! They seem to able to merely quote from their
scripts and not offer any original thought!!

I am particularly interested in getting sound from my CDs, DVDs, LPs,
and tapes onto the PC for further processing. These jacks seemed to
be the answer but I can't seem to get them to work.

Thanks for your responses (please use email as well).

Marty Troum
mtroum(removespam)@adelphia.net