Sound Card not working anymore

Hello,
I just got my pc fixed because it had so many viruses. Well, the guy reinstalled an operating system and now my sound card doesnt work. I cant find my original cd. What do I do? I don't want to really go out and buy a new sound card. Tried downloading from Emachine's website, but didn't work. I have a Emachine T3418. Also, now I keep getting runtime errors. I cant even pull up music to my media player. Please Help!!!!!!!