It's very hard to help you without knowing alot of information about the web-cam and your computer.
Simple solutions that could work:
- Is it plugged in correctly, and into the correct socket.
- Does your webcam have any drivers that you need to install? (Would of come on a CD with the webcam)
- What are you trying to use your web-cam with? (Skype?)
- Is your web-cam certified to run on your computers operating system? (An operating system = Windows 7, Vista, XP - Apple OSX, or Linux)
Please read the manual that you should of received with your webcam, it may be able to help you figure out what's going on.