A quick discovery when using the volume control and On Screen Display does not work.
I had this problem on my Acer Netbook Aspire One. After hooking it up to an external monitor, I found that the OSD (On Screen Display) did not work any longer when changing the volume up or down. This lasted a couple of months, the Acer Support site had no real answers other than to do one of 2 things. Make sure “Launch Manager” was using the latest driver and was actually activated. Anytime you re-start your machine it should start LM (launch manager) by default; I did download the latest driver and still no joy. The other Acer Support suggestion was to “”system will need to be restored back to factory defaults using the eRecovery software or Recovery media”, well, I didn’t need the OSD that bad.
After playing around on the Acer one day, I discovered somehow “Color Quality” setting was at 16bit instead of 32bit. I went ahead and changed that to 32bit, and like magic the Volume OSD started working again. I tested this several times and yes, this was the cause for me…
Good luck… Rick