You can free download the latest version of Realtek High-Definition (HD) Audio Driver from the link given below. To install the driver, follow the instructions given below. For hp laptops you can get audio drivers in this link http://hp.theinfiniteinfo.com/search/label/download-audio-driver
Supported Operating Systems: (Both 32-bit and 64-bit
Microsoft Windows Vista
How can I tell if my Windows operating system is 32-bit or 64-bit?