Necessity breeds innovation.
If Microsoft stopped shipping their OS to Europe, we'd be forced to make our own OS, and it would ultimately become a major competition to Windows, which in turn would cripple Microsofts stranglehold.
Microsoft isn't the only brain in the world, capable of developing a good OS.
They like buying up or invest heavily into its competitors (Apple, Novell).
If Microsoft stopped shipping their OS to Europe, we'd be forced to make our own OS, and it would ultimately become a major competition to Windows, which in turn would cripple Microsofts stranglehold.
Microsoft isn't the only brain in the world, capable of developing a good OS.
They like buying up or invest heavily into its competitors (Apple, Novell).