Not sure what operating system you are using, but a quick Google search came up with this:
Sony does not offer audio drivers for this computer.
However, they do offer this:
Problem/Question:Err Msg: Cannot play back the audio stream: no audio hardware is available, or the hardware is not responding.
Solution/Answer:Please check if there is any exclamation mark (!) displayed in Sound, video and game controllers under Device Manager. If there is any exclamation mark (!) in the Sound Driver Devices, please reinstall the sound driver with the steps below:
1. Start up the computer.
2. Insert the last disc of the set of Recovery CD-ROM into the CD-ROM/DVD-ROM drive.
3. Double-click My Computer and double-click the CD-ROM/DVD-ROM drive
4. Double-click the VAIO folder and search for the Audio folder in the Device folder.
5. Double-click the Audio folder and double-click Setup.exe
6. Follow the on-screen instructions to install the Sound Driver.
7. After the installation is completed, remove the Recovery CD-ROM from the drive and restart the computer.
* If the problem persists after reinstallation of the Sound Driver, please follow the steps below to check if there is any latest device driver upgrades:
In the Downloads section, please select Notebook and proceed with the steps below:
1. Move the cursor to the relevant Notebook Series and click the model of the VAIO computer.
2. Locate any latest Sound drivers and proceed as per instructions on the screen.
* If the problem persists after performing the device driver upgrade, please contact the local Sony VAIO Helpdesk. For more information on how to contact your local Sony VAIO Helpdesk, please refer to either Customer Service Guide or Warranty Card that comes with the computer, or visit the Support Network of the VAIO website.