How do I take out my operating system and re-install an update?

Using your recovery disc, AFTER backing up your data, would be the advisable route to take.

What are you trying to do? You do not take out the OS to install an update. You just download and install it. If you will explain everything a little better someone can help you. DrTom4444

If you want to uninstall an update, go to Start menu --> Control Panel --> Add/Remove Programs (XP) or Programs and Features (Vista/7) and select View installed updates (Vista/7) or check "Show updates" (XP) and remove the update that way. Otherwise, you can go back to Windows Update to reinstall it from there.