I have a problem with my sound. I use to have Realtek Audio drivers that worked now for some reason automatic updates has given me NVidia HDMI drivers. I don't have a NVdiia sound card but I do have a NVidia graphics card. When I uninstall the NVidia drivers and restart my computer it reinstalls them. My Realtek drivers don't work anymore. I just want onboard audio working again. I went into bios and it states I'm using onboard audio.

Maybe these articles can help.

Speakers and audio output not working after 10.6.4 update - CNET (http://www.cnet.com/news/speakers-and-audio-output-not-working-after-10-6-4-update/#)!

speakers changed after update - Bing video (http://www.bing.com/videos/search?q=speakers+changed+after+update&qpvt=speakers+changed+after+update&view=detail&mid=58573F24441E0FE7C5DE58573F24441E0FE7C5DE&FORM=VRDGAR)

speakers changed after update - Bing video (http://www.bing.com/videos/search?q=speakers+changed+after+update&qpvt=speakers+changed+after+update&view=detail&mid=4397EE2CCDA6162B90044397EE2CCDA6162B9004&rvsmid=58573F24441E0FE7C5DE58573F24441E0FE7C5DE&FORM=VDMCNR&fsscr=0)

speakers changed after update - Bing video (http://www.bing.com/videos/search?q=speakers+changed+after+update&qpvt=speakers+changed+after+update&view=detail&mid=A0B8DF88CABD0E047069A0B8DF88CABD0E047069&rvsmid=58573F24441E0FE7C5DE58573F24441E0FE7C5DE&FORM=VDMCNR&fsscr=0)

Well you just reminded me why I have windows automatic updates turned off. It's not that big a deal to do it myself every month or so. Never, I repeat, Never let MS decide what software for hardware drivers to install. Now you know why. I have been screwed in the past with creative audio updates from them and lan driver updates that caused both audio and lan to fail. I don't trust them over an actual download from the manufacturer of my hardware specific to my model number. You can try to do a system restore to wipe out what they did but choose the right one and do it from safe mode (hit F8 repeatedly during startup and if it takes you to a screen to choose which drive to use, choose your boot drive and immediately hit F8 again after). Criticals and Important updates OK, but never hardware or software. At the least select automatic download but let me choose if you need it to be automatic.

In my review of my past replies I realized I didn't really answer your question. In the event someone else also runs into this issue there is this. Open the Control Panel and set "view by: to small icons and click on Realtek HD audio Manager. On the top right drop down the "set default device" and select Realtek as the default device. I'm not sure what the difference is between default device and communication device mine seems to be the device not communication.

here is a page with more detailed information:
http://www.digitalcitizen.life/how-change-default-playback-recording-audio-device?page=1