Hi Shahrukh504,
I would recommend, installing the chipset drivers on the computer and webcam drivers as well.
Chipset :http://dell.to/QHpdvi
Webcam : http://bit.ly/i8RkJO
Also, run diagnostics on the computer. Below link would help you to run diagnostics on the computer:
From the above link select “Component” and select Camera and run diagnostics.
Kindly private message me the service tag of the computer, so that I can check for the correct drivers.
I am sending you a private message as well. Click on “Inbox” to respond to the message and provide system’s Service Tag and contact details so I may access your system records and check for further course of action. You could also click on Start Conversation to send a private message.
Awaiting your response!