mic is picking up sound from line out.

Hello, I recently reinstalled XP onto my PC. My mic used to work fine. But now, if I have any sound output coming from my speakers (even if the speakers are volume all the way down) it records in my mic. My mic is plugged into my line in jack on the front of my PC.

I don't know about my drivers and what not. I just know that I have an HP Pavillion a6432f PC.

please help!

Thanks