click START > type Device > Click Device Manager > look for imaging devices
Is your camera listed under imaging devices?
If it yes: Does it have an exclamation mark ! next to it? Right click the camera > click Properties. Is there an error/stop code listed?
If it is in the list, and there are no warnings, and properties shows that it is working properly, There may just be a Skype settings issue. Is there another application that uses the camera that you can try? Does it work in this other program?
If there are no imaging devices listed in device manager, your camera or USB may be malfunctioning or the camera has come unplugged.