How to Restore Hidden Updates (Windows® Vista)
  1. Click Start, click Control Panel, click Programs and Features, and then click View installed updates.
  2. Select the update you want to install.
  3. Click “Restore.”
  4. When the “User Account Control” dialog appears, click “Continue.”


How to Apply Security Updates Manually
  1. Click Start, click Control Panel, click Programs and Features, and then click Check for updates.
  2. Once the checking process is completed, click "View available updates."
  3. After confirming that "Security Update for Microsoft Windows (KB2803821)" is included in the available updates, click "OK" button placed at the bottom of the window.
  4. When the “User Account Control” dialog appears, click “Continue.”