Error message when you run the GPMC snap-in after you install Windows Vista Service Pack 1: “MMC could not create the snap-in”
You install Windows Vista Service Pack 1 (SP1) on a computer that is running the original version of Windows Vista. When you try to run the Group Policy Management Console (GPMC) snap-in, you receive an error message that resembles the following:
MMC could not create the snap-in.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB954375.