|That's not much information to go on, but let's give it a try.|
Have you loaded the webcams drivers/software?
Are there any yellow exclamation marks showing in device manager?
Does the webcam work when not using Skype?
Is it a built-in cam, or an addon? What brand/model?
Answer these questions and we might get somewhere.
Please let us know if you found someone's advice to be helpful.