Windows XP

• 1). Click the Windows "Start" button and click "Control Panel." Double-click the "Security Center" icon to launch the Windows Security Center.
  
  
• 2). Click the "Automatic Updates" button. Click the "Automatic (recommended)" radio button to turn on the feature. Select the frequency and time to automatically search for and download updates.
  
  
• 3). Click "Apply" to save the changes and click "OK." Close the Windows Security Center. Windows will automatically search for and download available updates from the Microsoft server.
  
  

Windows Vista

• 1). Click the Windows "Start" button and click "All Programs." Scroll up and click "Windows Update" to launch the update console.
  
  
• 2). Click "Change Settings" and select "Install updates automatically (recommended)" under "Important updates."
  
  
• 3). Click "OK" to save the changes.