Hi,
It does not make any sense. Based on its support page, it uses "Conexant HD-Audio SmartAudio 221 Driver" for Vista
and now it can't see for Windows 7:
https://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?cc=us&lc=en&dlc=en&softwareitem=ob-75899-1
Please try the following methods:
http://windows.microsoft.com/en-US/windows/help/no-sound-in-Windows
Regards.