How do I delete a shape within a shape, drawn with pen tool?

Thank you!

I won't understand what's happening..

I tried your suggestion earlier and it worked but since then it just won't work..

I create a shape and fill it black. 

Then create another shape inside that shape.

Then I click on the subtract icon in the pathfinder window..

and nothing happens!

Yet it worked earlier..

Any idea what's going on?

That was it! 
I just realised that a moment before you posted..

Thanks again..