Click the metronome icon at the top (its the traingle looking thingey), make sure PC speaker is checked, then also check whether you want it the click during recording or playback or both...try this and let me know....
I asked Flavio about this, and he said something about how by pc-speaker he meant the little speaker you can attach directly to your motherboard. I don't see how that's going to help anyone recording off a mic. Looks like the metronome is geared towards midi users.