Can't Record Via Mic on Win7

I've got a Dell Optiplex 760 running Win7 and I can't record from a mic using either the back sound port or one of the two front USB ports and a plug in sound card.

The machine has integrated MAX onboard sound and currently two sound cards that it can see and device manager reports: both 'USB pnp sound devices'.

One of those USB pnp's is a 'guitar link' plugged in there. It works fine with Guitar Rig.

The other one is the one I want to use to record through with a mic.

The 'recording device' screen shows five devices:

Microphone 4USB PnP sound
Microphone Sound Max Integrated
Rear Input Sound Max Integrated
Stereo Mix Sound Max Integrated
Microphone USB PnP sound.

I can't get the mic to work on any of those. I can only enable one at a time and I've done that and checked each one, no luck.

I don't understand the three 'sound max integrated' things. I guess the 'rear input' is the back port I'm trying to input the mic through and which doesn't seem to work.

But what are the other two? As selectable recording devices? I guess one of them would just mean select onboard sound card as the recording device (leaving open the question of how to access it. maybe internally only?). But that leaves the third one. what's that about?

Anyway. I'm thinking basically the system should be/would be very simple.

But it's got me going round in circles. Don't know if it's the computer hardware is wrong, or the software is wrong, or my configurations are wrong.. what?

So I'm seeking advice.

How should I set it up so's it certainly should work and I can know that if it doesn't this, that or the other is wrong?