After I installed Windows 7 beta on my HP Pavilion DV6500, I was not able to use some of the audio features like the front headphone audio-out jack, microphone audio-in jack etc. This is because of the old Realtek HD Audio Driver which was not compatible with Windows 7.
Realtek has added support for Windows 7 and you can download the new version R2.16
Update (May 7,2009): It doesn’t say Windows 7 in the link, but the update is primarily due to Windows 7. At this time of update, they even have newer version of the driver R2.22 updated on 4/20/2009. So the link just says, Vista Driver (32/64 bits) Driver only (ZIP file)
This supports Windows 7, Windows Vista, Windows XP and other earlier OS for both 32-bit x86 and 64-bit x64 OS
They also have ATI HDMI Audio Device driver and 3D SoundBack which restores audio effects, including surround sound, reverberation, and spatial effects, for legacy game titles when running on Windows Vista.