In some of the sound cards integrated into laptops' mainboards (here: Realtek HD in Dell Vostro 1310), the option to hear (in the speakers) the sound which comes from the microphone input (or even line input) is not available in Windows.
The microphone itself (both internal and external) works correctly (ie. the voice can be recorded), however, the ability to use system mixer to combine sound from music file and a sound from external input (line in or microphone) is not provided by the system (Windows XP).
Is there a solution (possibly a driver hack or registry hack) to this problem?
I am not willing to buy a separate hardware mixer to achieve this simple goal.