Headset mixing all output sound and microphone sound

Hi,

My friend has a Razer Carcharias headset and a Realtek onboard sound card in his computer. We tested the headset on two other computers and it works very well. When we tried it on his computer, it wasn't the same story.

For some reason, the microphone input is mixing with ALL the audio being output from the computer. In Skype, for example, when he plays a song or is in a game you can hear everything he's hearing as well as voice. I tested it in sound recorder, and it does the same thing. When you play a song and talk into the microphone, it records both. I've gone into the Realtek settings and tried changing every single audio channel as well as reinstalling the drivers but to no avail. I know it's not the headset because we tried it on other computers and it doesn't do this.

But what I don't get is if all the output sound is mixing with the microphone sound and being fed back in, then shouldn't there be an echo in Skype when someone talks? When I talked with him over Skype I didn't hear myself echo, but I did hear when he played a song or started a game.

The computer is an HP m7640n
http://h10025.www1.hp.com/ewfrf/wc [...] ct=3245032

Sorry, I couldn't find any setting like that.

I'm thinking we should just put in a sound card and use that because I have no idea why it's doing this.