It sounds like to me that he did a re-install and forgot to install the sound drivers as they are not included in a reinstallation.

You need to visit the manufacturer's website and under support/downloads/drivers using your model number you will find a page with a list of all driver files that was installed from factory onto your computer. Look for the audio files and download them to your desktop so that they are easily found.
open the icon that you downloaded and it should auto run to install the driver files to your computer.

start > rgt. clk. My Computer > choose properties > choose hardware tab > choose device manager button
In the new window look to see if there are any ! (yellow ! ) or x and click on them to bring up the properties box....select drivers tab and then select to uninstall driver ....follow the prompts to do this.

Restart your computer and windows will install the proper drivers to get your sound to work...