Windows Service Pack Blocker tool
Hi, just found out about this article and amazing tool-kit to block SP installations! A blocking tool is available for organizations that would like to temporarily prevent installation of Service Pack updates through Windows Update. This tool can be used with:
This toolkit contains three components. All of them function primarily to set or clear a specific registry key that is used to detect and block download of Service Packs from Windows Update. You only need to use the component which best serves your organization’s computer management infrastructure.
When the '/B' command line option is used, the key value name 'DoNotAllowSP' is created and its value set to 1. This value blocks delivery of a Service Pack to the computer through Automatic Update or Windows Update. When the '/U' command line option is used, the previously created registry value that temporarily blocked the delivery of a Service Pack to the computer through Automatic Update or Windows Update is removed. If the value does not exist on the computer on which it is run, no action is taken.
Note that the executable and script have been tested only as a command-line tool and not in conjunction with other systems management tools or remote execution mechanisms.
Please note that this toolkit will not prevent the installation of the service pack from CD/DVD, or from the stand-alone download package. This simply prevents the service pack from being delivered over Windows Update.
Download from here.

Well if you choose not to update your computer then you may try this tool. It is not advicable to block windows updates. If you have a virus attack on your computer then you will not have an answer. Please be carefull before using such tools