1.Check that your webcam is switched on and is connected to your computer.
2.Close all programs that may be using the webcam. These include video editing software, instant messengers (such as Yahoo Messenger or Windows Live Messenger), browsers, Windows Explorer, and even some websites.
3.Make sure that both you and the person you are video calling are using the latest version of Skype, Yahoo Messenger..
4.Make sure that you have the latest version of Microsoft DirectX. For Windows Vista and Windows 7, you can get the latest version of DirectX by updating Windows with the latest service packs and updates
. For Windows XP, you can download it here.
5.Check that your webcam is listed in Device Manager
Do one of the following:Windows 7
: Click the Windows button and select Control Panel.
Click Hardware and Sound and under Devices and Printers select Device Manager.
Click the little arrow beside Imaging Devices.Windows Vista
: Open the Start menu and select Control Panel.
Open System and Maintenance and click Device Manager.Windows XP
:Open the Start menu and select Control Panel. Open System and in the Hardware tab, click Device Manager.Under Imaging devices, check that you webcam is listed
If it's not listed, reinstall the drivers for your webcam.
A driver is the program you install with the webcam which makes it work on your computer. (Some webcams use preinstalled drivers so you may not have had to install one.) Make sure you have the most recent drivers for your webcam by downloading them from the webcam manufacturer's website.
Please let me know if you need further assistance on this issue .And try to include more information in your request ...like camera model # , operating system ( windows xp ,vista ,7, etc ...) , and the software you are using to chat online ..(yahoo messenger, skype , facebook,or any other platform ...)