How do I adjust laptop audio to specific programs?

How do I adjust laptop audio to specific programs?

I have hooked up my laptop to the home stereo via an external sound card (RealTek). It works great for playing music but I was wondering how I may select for the laptop computer speakers to still be used for certain computer functions like log-in sounds, playing video clips, etc.

I've heard the laptop speakers work on little test functions in the control panel but can't get any other use out of them.

Thanks.