When I open web cam its shown error ie, Webcam driver open fail. please restart camera or computer?

I think there are two reason why that show it can be that the installation of the webcam is not properly installed in the computer or it is your computer that has a problem. To test try using other camera that you know and confident that is working from other computer and try it on your computer if that works the problem is your camera if the camera still don't work then the problem is in your computer.