Windows Update is a service provided by Microsoft that provides updates for the Microsoft Windows operating system and its installed components. These security updates are delivered on the second Tuesday of each month, Patch Tuesday, but security updates can be delivered whenever a software update is required to prevent an exploit targeting Windows users.
Windows Update can be configured to install updates automatically, ensuring that a computer is always up-to-date and not vulnerable to computer worms and other malware.
Windows 7 and Vista provide a Control Panel to configure update settings and check for updates.
To check your update settings in Windows 7 and Vista
Click on the Start or Windows Button and choose Control Panel from the menu, then from the new Windows choose System and Security, then click on Windows Update.
From here you can see when your updates will install and update settings by clicking on Change Settings.
You can then set when to install updates, whether to update automatically or just be informed and what updates to download.
If you have some updates it will show on the main Windows updates screen and give you the option of installing now.