Another tidbit from Mena Paton:

 

Are you or your users not happy to see Groove starting up every time you restart your system?  If so, end users can easily stop this Groove behavior by opening the Groove Options menu and selecting Preferences, clicking the Options tab, then clearing the setting: Launch Groove when Windows starts up.

 

If the setting change doesn’t hold through the next system restart, an administrative policy may be over-riding the end-user setting, mandating Groove startup whenever users come online. This enables Groove to promptly synchronize Groove workspaces as soon as users come on line so that team members can all be kept up to date. But if you use Groove infrequently, this setting may not be necessary and can be disruptive since Groove utilizes system resources to update spaces with information that may not required. Groove administrators can change the policy override where appropriate by modifying the Active Directory policy that overrode the end user setting.