Windows Service Pack Blocker Tool Kit temporarily prevents installation of Service Pack updates through Windows Update that is valid for 12 months following general availability of the service pack.

This toolkit contains three components.

1. A Microsoft-signed executable – creates a registry key on the computer on which it is run that blocks or unblocks the delivery of a Service Pack to that computer through Windows Update.
2. A script – does the same thing as the executable, but allows you to specify the remote machine name on which to block or unblock delivery of Service Packs.
3. An ADM template – allows administrators to import group policy settings to block or unblock delivery of Service Packs into their Group Policy environment. Administrators can then use Group Policy to centrally execute the action across systems in their environment.

Download: Windows Service Pack Blocker Tool Kit

Essentially all three components perform the same task and will block Service Pack 1 (RTM) of Windows 7 and Windows Server 2008 R2 that is expected to deliver in Q1 of 2010. You can do it manually as well by editing a simple registry value, just do it as mentioned below:

1. Run Registry Editor (Regedit.exe) and go to: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\WindowsUpdate
2. Now create a new DWORD value called DoNotAllowSP and set the data 1
3. Finally close Registry Editor and restart your Windows to take effect.

Note: It blocks Service Pack updates through Windows Updates only.