virtualbox.org

I am a newcomer to Virtualbox so pardon any misunderstandings.
I have setup virtualbox in my Windows 7 64 bit Host machine and have installed a Windows 7 64 bit Guest successfully.
However the guest machine reports that 'No Audio Output Device is installed'.
I have gone to the settings and checked that the audio is enabled and the audio controller is ICH AC97 and the Host Audio Driver is Windows DirectSound.
Rebooted without success.
I have gone to the Device Manager in the guest and under other devices there is an entry 'Multimedia Audio Controller' but I am unable to determine the correct driver to choose and none is found using the update driver option.
The host reports for audio in the device manager a 'High Definition Audio Device'.
The driver details for which are
dmk.sys
HdAudio.sys
ksthunk.sys
portcls.sys
SysFxUi.dll
WMALFXFGFXDSP.dll
all from Microsoft.

How do I get sound to work in my guest Windows 7?

This has been covered hundreds of times here.
You need to start the guest and go to realtek.com.
Download and install the drivers and reboot.
Then force Windows 7 to do an update.
Reboot again. (Hey it a Windows thing)

Thanks for the reply. I had searched the forums for 'no audio output device installed' but the results were negative. I did find a lot of entries talking about no sound and the instructions to instal the drivers was noted. I apologise if I caused you any trouble in replying to what you might think of as the hundred and first time. I think you might agree that I did provide all the information and had searched for an answer.

Searching for "Windows 7 audio" (you can add the 'driver' part too if you want) should have given you plenty of results.