This toolkit will stop IE8 from installing itself on your system through Windows Automatic Update.
IE8 will be officially available through Windows Update in April. By that time, IE6 and IE7 will be automatically updated to IE8 if you choose to install the updates automatically. You do have the option to choose to install your updates manually and uncheck the IE8 update, but that might also mean that people who don’t want to install IE8 yet might accidentally miss that step and got it installed.
The safe way to do this is to use Microsoft’s Blocker Toolkit. This Blocker Toolkit is intended for organizations that would like to block automatic delivery of Internet Explorer 8 to machines in environments where Automatic Updates is enabled. The Blocker Toolkit will not expire.