I know this is an old post but people may still be looking for an answer, and I have found it.
About two or three months ago my left speaker in the laptop died. It did not bother me because most games and music seemed to sound just fine with one speaker. Movies and such usually get routed through the headphone jack to the surround sound system. But today I wanted to listen to a podcast and there was no sound.
Windows volume meter showed there was in fact something playing but it was not coming out the right speaker. I tried playing something else and it played fine. So I figured that the pod cast must be playing only out the left channel. So started my quest, to set windows 7 up to play sound in mono. Going to playback devices and configure for the speaker only had a stereo setting.
I have a realtek driver loaded and nowhere could I find a mono setting.
So I finally ended up at the realtek site and downloaded a generic vista/win7 driver.
It did not want to install because the driver was not signed. I uninstalled the old driver. I tried again to install the generic driver I had just downloaded without success. So finally I decided not to use the
setup.exe and instead double clicked on
alcupd.exe (the driver update program).
Only thing is that because I uninstalled the laptops sound driver, I no longer have any of the environment or equalizer settings. Not a big deal for me, If I need them I will just re-install the laptop sound drivers. So I right click on the speaker icon in the taskbar and choose playback devices, then the properties for the headphone. I renamed headphone to Internal Speaker.
Then under enhancements I chose Headphone virtualization. Success, now can hear both the left and right channels on the one good right speaker, with just slightly less volume.
I was able to hear my podcast just fine with the new settings.
So I guess "Headphone virtualization" equals Mono sound. Hey it works for me, maybe it will work for you.