Stero doesn't work on computer...

Hello,
Recently I got a virus on my computer and had to restore everything on my computer.
Everything works great except my speakers and headphones wont work. I went to control panel to sounds and audio device and it says there's no audio device. But my speakers are plugged in and turned on the Max. I've had the same speakers since I bought the computer in May of 07 or 08. It's a Dell windows XP. I've never had this kind of problem before. I've tried plugging in just headphones and it still doesn't work. Is there something I need to download to fix this? I miss being able to listen to my music and watching youtube so please help.