Realtek HD Audio mic playthrough problem in Vista

System:

Acer Aspire 5315 laptop
Vista Home Basic 32bit SP1
Realtek 268 HD Audio (inbuilt)

I've been attempting to use this setup to record audio, and keep running up against the same issue. How do I monitor microphone input (either from the inbuilt mic or the 'pink in' socket) whilst recording? There doesn't seem to be any way to enable this function, the result being that I can only hear what I'm recording by playing it back afterwards.

On most other systems, you can normally monitor mic and/or line-in input by simply clicking on the system tray speaker icon to get the mixer, then turning up the relevant slider. It seems that this option is now simply unavailable. All I get on the Vista mixer is volume controls for the speaker, Windows sounds and whatever applications that happen to be running at the time. The Realtek control panel has options for 3D sound, mic boost, default sample rates etc, but no mixer and no option to enable playthough for the mic.

I've tried a number of drivers, including the latest updates from both the Realtek and Acer sites, and also some older versions. While there are differences between these drivers, none of them seem to provide the option I need.

Having Googled this issue, it seems it is a common problem. A few places (like this one give a workaround that involves changing a Registry setting. However, the settings given don't correspond with what I have on my machine. I've tried speculatively tweaking a few likely-looking things in my registry, but to no effect.

And yep, I've tried all the obvious fixes:

- In "Sound>Playback>Speakers Properties>Levels", there are only volume sliders for "Realtek HD Audio output" and "PC Beep", nothing else. Both set to full volume.
- In "Sound>Recording>Microphone Properties>Levels", the "Microphone" and "Microphone Boost" sliders are set at full volume and the microphone is enabled.
- In both the playback and recording tabs, "Show Disabled/Disconnected Devices" are both selected. Changing default recording device from "Microphone" to "Stereo Mix" had no effect, so I put it back to mic.

Any ideas would be greatly appreciated.