This seems to be a common problem. I've tried everything I know. Sometimes the webcam works with Skype and sometimes it doesn't. Can you tell me how to fix it?
First, go to Dell Support page, identify your computer model and download and install the latest webcam drivers available. After that, upgrade your Skype version and try again. If the problem is not solved, install DirectX and check the troubleshooting guide provided by Skype Support Team.