1. Open Internet Explorer Web Browser (Windows updates cannot be done using Firefox or other non-MS browsers).
2. Under the Tools menu option, click Windows Update (If this option is not there then go to http://update.microsoft.com.
3. If any dialog boxes or messages appear asking to install an Active-X program from Microsoft, click "Yes" or "Install" and "Run." (This installs a tiny program from Microsoft that scans your computer for the needed updates.)
4. Click "Express" on the Microsoft Web Page in order to get "high-priority updates."
5. Click "Install Updates" if any are needed.
6. After it finishes installing, it may ask to restart computer. Restart your computer and repeat the above process until there are no more high-priority updates to be installed.

For the latest explanation of the Microsoft Update Service, please see the article, Use updating services from Microsoft to keep your computer current on the Microsoft web site.