Search for DMetro or get some stand-alone computer software metronome to your liking. Then in the control panel (at least w/ XP) go to sound, audio devices and select your Aardvark for default playback.
It will make you hear all your system sounds through your Aardvark (like for example your headphones if you set it up like that). Of course this sets it up to play all system sounds through but when you're recording its not like you're going to be playing games or listening to music.
Hope this helps you.