How to Disable Windows Messenger Service:
If you're getting
popup spam in a gray window on your desktop
then you need to disable Windows Messenger Service.
1) Right Click on My Computer and choose Manage
2) In the window on the right choose "Services and Applications"
and then choose "Services."
3) Scroll down and find "Messneger, and right click on it and choose "Stop"
4) Right Click on it again and choose "Properties."
5) Use the drop down menu to set the startup type as disabled.
That's it!