There are few things more important to your Windows computer than keeping your operating system (OS) software -- Windows XP, Windows Vista and Windows 7 in most cases -- up to date. Out-of-date software can be insecure, unreliable or both. Microsoft releases regular updates on a monthly schedule. Manually finding and installing them, however, would be a big chore, which is why Microsoft includes Windows Update as part of the OS.
Windows Update is set to automatically download and install updates by default. I strongly recommend leaving these settings alone, but there may be times when you want to disable automatic updating, or for some other reason it is turned off and you need to turn it on. Here's how to manage automatic updating in Windows 7 (articles already exist on how to do this for Vista and XP).
First, click the Start button, then click Control Panel on the right side of the menu. This brings up the main Control Panel screen. Click System and Security (outlined in red.)
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