It`s not as simple as saying my sound card does not work is it.
How do you expect an answer to your problem, we need to know the make of the sound card. If it is integrated as part of the motherboard of the computer you are using.
We need the brand name of the motherboard, eg: Asus and it`s board model number Eg: Asus M2N-SLI-M an example. to even hunt the driver down for the onboard sound for example.
And also what Os or version of windows is running on the Pc, plus is it a 32bit version of the Os or a 64bit version of the sound driver.
There all the details you need to find and post to have any chance of getting the sound to work.
Think man. If I asked you why my wall was only 4ft high could you tell me the answer as to why it is ? Or are you left down to guessing the problem of why it is, and the reason ?