recording with speakers muted

I have an xp machine that lets me record with the speakers muted.

I also have a vista machine that let me record with audacity with the speakers muted.

I recently had to re-install the os on my vista machine and now I can’t record with the speakers muted.

I have no idea why my previous vista os installation allowed me to record with the speakers muted. I’ve googled the problem without success.
If you can help, what do you suggest?

I can currently record with the volume un muted.

Updating the driver led to a solution.

Windows XP lets you record computer playback without hearing it because there is a separate master volume slider you can turn down without turning the wave output slider down.

Windows Vista and 7 normally cannot record computer playback silently using the built-in sound device “stereo mix”. See . Some special drivers may capture the sound before it gets to the sound device, meaning you can turn its output down.