SOUND, AUDIO MISSING OR NOT WORKING COR...

though itz unclear to me of wat os u r using..
assuming that u r using win xp pro sp2..n directx installed..
check if Audio device is enabled in bios..

howevr, download microsoft kb888111 update n install it..u need to re-install or update the device driver (may b manually)..logon to internet n seek the package/audio driver..along wid the company, there will b a list of such site n driver download links if u search by the model name on a search engine like google..
download them onto a location; if the driver is in a zip format, unzip it,if itz in .exe form, just run it; if done manually it'll ask for the correct driver and location; relocate the path and a .inf file (wat it'll ask for)....goto the device manager n verify, if installed properly..!!
also download n install k-lite mega codec pack....

if not fixed try using a standby pci snd card (in such case it'll b a confirmed case of ur system board is likely to b defective)..
but always better to consult ur system admin/vendor....

This is comon in pc's that you format and reinstall the windows (vista , xp , 2000 , nt , etc)or the operative sistem , the unique solution is that you need to enter to the page of the fabricant of the machine (hp , dell ,etc...) and find a link that says ''support and drivers'' put the code of the product and download all of the drivers for your operative sistem .
remember , all the drivers if you search in a correct way you can find it free