Is your computer's sound card not working? Try going into Windows device manager then right clicking and deleting this audio device. While still in device manager there is a refresh icon that will make Windows XP scan for hardware changes.
Windows will then see your audio device again and try to install drivers for it. You might be prompted for your Windows installation media. You can use that CD that came with that computer or an audio device.
You can also have that computer connected to the Internet and if you have Windows updates configured, you can select to download those drivers via Windows updates. This fix originally was successful on a Toshiba Tecra M2. This fix can be tried on all versions of Windows, from Windows 95 to a current Windows 7 and 8.
You can try this fix on desktop computers as well as laptops.