Looks like Google is doing a Microsoft-related search and probably Microsoft is paying them for this special search feature.
Try and visit www.google.com/microsoft.html and see for yourself.
From the Inquirer:
… as further proof that the two are definitely secretive partners in crime, you can get to the search page through Microsoft (http://go.microsoft.com/fwlink?linkid=23818). Kind of strange when you take into consideration Big Steve Ballmer’s mindset on Google, isn’t it?