Microsoft Silverlight is an application for running media-rich browser plugins or applications. If your installation of Silverlight is configured to install updates automatically, then no further action is required, because Silverlight will have been updating itself in the background ever since it was installed. But if you have it configured to let you choose what to install, or to never check for updates, then you can update Silverlight using the Windows Update utility. Silverlight updates are typically downloaded alongside other Windows system updates, so it is possible that you have already been updating Silverlight without knowing it.
Open the "Start" menu. Type "Windows Update" into the search box and press "Enter" to launch the Windows Update utility.
Click "Check for Updates." If an "important/optional updates are available" link appears, click the link to view the updates. Silverlight updates are usually marked as important.
Check the box beside the Silverlight update. Click the "Install Updates" button. The installation time varies depending on the size of the update. Windows notifies you once the installation is complete. You may need to restart your computer to complete the installation process.