Windows update is also pretty good about installing a driver that screws something up. If you just recently did a windows update and under optional updates you selected a driver install for your sound card that could be the problem. In Device manager is there a yellow exclamation point or red circle where your sound card hardware is??? if so you may be able to do a driver roll back to get it working again. Feel free to click on my sig and give me a call and I will help you over the phone if I can.....
Get that Hawg Outa There
Professional Computer Service \ Repair
iPhone, iPod, & iPad Repair.