This means the driver is faulty. You will need to fix this problem. There are two ways to do this. Attempt each in order.
Select the item in device manager and delete it. Then reboot your computer and let Windows re-install the driver (this will occur without any action on your part). Now try the webcam and see if the problem has been resolved. If not try 2.
Ensure that you have your laptop install DVD to hand. If not, go to the Dell website and download the Webcam driver for your Laptop. Now open Control Panel and (Viewing by category) select the look for any item which mentions your Webcam a double click to delete. Check that all similar are removed, then reboot your computer and run the driver re-install program.