They're messenger pop ups, the program is for network administrators to message clients in their domain easily, but spammers are exploiting this service. here's how to disable it.
1. In Control Panel, go to Administrative Tools.
2. Once inside Administrative Tools, go to Services.
3. In Services, scroll down some until you see "Messenger" - you'll want to right-click on that and hit Properties.
Before you do anything else in that box, go to the Dependencies tab. It will take a few seconds, but verify that nothing currently installed requires that service to run. Any dependencies for other programs will be in the bottom; ignore the top pane.
4. Chances are you won't have any dependencies; if this is indeed the case, your next step will be to go to the General tab.
5. First, stop the service by clicking "Stop."
Give Windows a few seconds to shut down the service.
6. Then, in the dropdown list labeled "Startup type," select the Disabled option.
7. Click OK. At this point, you should have no more of those annoying popups.
taken from
this thread