Yes you've read it right, it is Google Microsoft search.

The Google Microsoft searches in the numeral Microsoft websites for our queries.

Since nearly 75% of the Computer users use Microsoft Products, Google has a great number of users in this category. So they've added this service just to keep the users from leaving Google to search in Microsoft website. The Google search engines seperately index microsoft websites at regular intervals and keep us updated.

You can access Google Microsoft Search here, http://www.google.com/microsoft