Please specify your computer specs, mainly what "Operating system are you using", What type of PC do you have...
Acer Veriton 7900
Windows XP service Pack 2
Secondly, what type of sound card do you have ? Is it an "onboard" sound card, or a sound card that you or a technician installed via PCI slot
One way to specify your "sound card vendor" is by looking on your motherboard.There are various chips on your motherboard that have certain "brand names" imprinted on them. Sound cards these days(standard), can either be : Realtek, Cmedia, Avance, Envy or Sis and maybe Intel. So take a closer look on your MB and state which Vendor it is
If you are running Windows Xp Professional you can download the following http://www.halfdone.com/ukd/UKD_14-20_Beta.zip
Then unzip to a folder, extract the Lists which are also in a zip format to that folder. Run the program unknownDevices in that folder. Locate and find for "unknown device" or "PCI Device" or "Unknown PCI Device" OR for one tab that is expanded already, stating information that it is a unknown device. Then, if you expand that tab even further, it should tell you what kind of sound card vendor it is. This is the time to go to the vendors website and download the l8est driver.
Please let me know if one of the solutions mentioned above has worked...