Click on "Start" and type "Msconfig" in the "Run" box at the bottom and hit "Enter". This will open the "System Configuration" window. Click on the "Services" tab. Scroll down to the "Group Policy Client" service. If it is "Running" then "stop" it. If it is already stopped then untick the box on the left to stop it starting at launch of Windows when you start the computer. Restart your computer and see if the message appears again.