Microphone on Laptop Problem

Hello, i want to use my laptop (windows vista) to create a karaoke machine. My laptop sound output is connecting to a Home Theater System port AUX 1. Basically, I want to output the microphone sound through the sound system together with the music. The problem is there is no sound from microphone coming out from sound system. The music does though. The microphone works well when I plug it into other desktop (windows XP).

I've checked all possible setting in control panel but without luck. Whe I tap the microphone, the green bar appears, but no sound coming out. Anyone can help me out please?

Thank you.