Many companies are waiting to deploy the Windows XP SP3 and Vista SP1 on their computers. In case you have the same target and use the Microsoft Windows Update or WSUS for the patch management, you will have to block these Service Packs on your computers otherwise will be automatically downloaded.
Some helpful information is in the Ghacks article, at the following link: Block installation of Windows XP SP3 and Vista SP1.
An intersting tip is to create a script with the reg modification and using DS server run on the target client where you need to block this update:
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate] "DoNotAllowSP"=dword:00000001
Remember that you can re-enable the Service Pack deployment on the Windows Update, simply by deleting the registry key. The next reboot will start the SP deployment.