Microsoft Windows Update helps you install all of the latest patches, upgrades and security fixes from Microsoft. These updates are important to keeping your computer running smoothly and fixing security holes that can allow nasty mal-ware into your computer.
Please note that these updates can sometimes increase the system requirements for your Windows Operating System. Windows XP needs a minimum of 512MB of RAM for Service Pack 2 or Service Pack 3. Computers with less than 512MB of ram will notice a significant performance drop when upgrading to Service Pack 2 or Service Pack 3.
EXTREMELY IMPORTANT: TO ENSURE THE SAFETY OF YOUR DATA ON YOUR COMPUTER, BACK UP YOUR HARD DRIVE BEFORE DOING ANY SERVICE PACK UPGRADES. For more information on backing up your computer, see this article on making backups.
If you ever see this icon in your notification area:
You have updates you need to install. Click on the yellow shield.
This appears:
Click 'Download'.
The updates will automatically download and install. When they are done installing, you will see the following screen:
Click on 'Restart Now'. Don't do anything else with your computer until after it restarts.
That is how you do Automatic Windows Updates