How to Update Windows Vista
Instructions
1Click on the "Start Menu" and select "Control Panel."
2
Click on "Check for Updates" under the "Security" section in the control panel. This will take you to a new window.
3
Click on "Check for Updates" near the window's upper left-hand corner. This will begin an automatic search for new Vista updates.
4
Make sure all other programs are closed and click on "Install Updates." Vista will automatically download and install the updates. A progress bar indicates how far along the update process is.
5
Wait for all updates to finish installing. Do not turn off your computer during this process. Depending on how many new updates you need to install, the automatic updating process may take minutes or hours. When complete, restart your computer.
Source...