I know this is an old thread, but I wanted to post something I found while having similar issues.
I recently purchased a headset from Turtle Beach (MW3 Call of Duty). The installation was as simple as connecting the USB cable and power to the device and the headset started to work very well. However, I could not get sound to my regular speakers after that. The speakers are plugged into the green audio jack in the back of the computer and driven by Realtek High Definition Audio sound hardware and drivers
. In the Playback devices area, the green bars rise and fall as if sound was being generated, but nothing would come out of the speakers. Clicking "Test" would either do nothing or give an error that "the device is in use by another application."
I read many forums and tried the following: update realtek drivers; uninstall realtek drivers and reinstall; disable Turtle Beach audio and restart; uncheck "Allow application to take exclusive control of this device"; uninstall the realtek software from the uninstall programs part of the control panel; and so on and so on...
So I finally got this fixed and wanted to share my findings in one of the forums in hope that others will "have one more thing they can try..."
Right click the speaker icon in the lower right tray and choose Playback Devices. Right click on your speakers that are not working and choose properties. Go to the advanced tab. Adjust the Default Format. In my case, it was not working at any of the "Studio Quality" settings. However, as soon as I dropped it back to DVD Quality (16 bit, 48000 Hz) it was fixed. I can now go in to the Playback Devices area and switch between the headset and regular speakers by simply right clicking one and setting it as default and right clicking the other and setting it as disabled. Just note that you might need to right click in a white area and check the boxes that let you see disabled and disconnected devices.
I hope this helps a few people that stumble on to this. Very frustrating problem...