When you right-click on a file in Windows Explorer and select “Open With...”, it pops up an option discover the appropriate application to open the file with by calling a Microsoft Web Service. I have never once actually used this option, so it simply adds an extra mouse click to the process (to dismiss the dialog). I've been meaning to find out if it was possible to disable this popup for ages, and finally got around to consulting the Oracle of Google.
It turns out to be quite easy - simply bring up RegEdit, navigate to
and add a DWORD value called NoInternetOpenWith to the registry key, with a value of 1.
Bingo, no more popup.