How to Stop the C000021A Fatal System Error on Windows

1. Open your browser and go to the Service Pack 4 web page on Microsoft's website (see the first link in Resources).
2. Click the 'Download' button. Wait for the download to come up or click the link mentioned on the new page for the download. Save the file to a directory you will remember if you choose not to open it right away.
3. Browse to the location you downloaded the file to and double-click it to open it.
4. Click 'Next' and follow the installation wizard. Restart your computer when the wizard completes your installation. Don't forget to save your work before restarting.