I'm having problems with my sound card

Hello there, i have been having problems with my sound card driver files,i can't seem to find the right one(FCC id:138-SN96116)it's a aztech,it works and and records and does everything else it is suppose to do but when i try to have a voice conversation with someone over MSN messanger it says "Error microphone is being used by another application or it's not working properly"i checked to see if another app was using it there is not,so it must be the incorrect driver files i think.....IF you could please help me out with this one great ,thanks