Soo, my friend got a new usb headset because the old one (not usb) is broken but when he connects it to his pc it causes the webcam to stop working, the webcam is still there on the pc but Skype and other programs says the webcam isn't working and you should try to close any other programs that are using this device.
If the webcam also has a microphone, it might be getting deactivated in favor of the one on the headset; perhaps that's killing the whole thing. Go into Device Manager and see what sound devices you have, and disable the one on the webcam (don't remove it, just disable it).
Did you load any software for the headset? See if it is trying to control the webcam and see if that function can be switched off.