The first thing to do is uninstall the sound card driver. Then with the computer off and unplugged, reseat the sound card. (wiggle it out then back in.) Plug in and turn on the computer. It SHOULD recognize 'new equipment' (the sound card) and go about installing the driver. If this works you are good to go. If it doesn't recognize the sound card see below.
I'm going to go out on a limb here and suggest that the sound card crapped out because it's unlikely that both speakers went bad simultaneously. If there was a lightening storm your 'puter was affected, and it just took out the sound card, consider yourself fortunate.
Unless you want to go super high end, sound cards aren't expensive and it's an easy DIY fix. I saw them online for $16 to hundred$. Or from +-$20 at BestBuy or WalMart.