We'd need some more info, like when you gave it to him ddi the box get banged around at all?. Have you opened up the case and tried re-installing the sound card and then re-installing it's drivers? what kinda board and such is it etc..
Go into control panel, click on systems, go into hardware, find your sound card driver. right click on it and select remove. it will ask you if sure about removing device, click ok or yes which ever comes up. then just reboot. the driver should reinstall and work. It may ask you for driver disk, so have it ready. If this is a sound card that came with pc then the driver is already in windows and will reinstall. If you still have problems turn pc off. take out card turn pc on, then after it boots turn back off. then put card back in, then turn back on. This will insure driver installs correctly. If you still have problems maybe someone else may have an opinion on how to fix it.