In my experience, I don't find myself lingering over the company logo. I see "Windows 2000" or "Windows 7" and kind of gloss over the word "Microsoft." Their product branding is far, far more prevalent than their company branding. This is an attempt to give the company itself more visibility. I'm a computer person, we are all computer people, so we all know immediately that Windows = Microsoft. Go talk to your average Joe, and they won't necessarily make that connection right off the bat.

Also, that's a pretty cool logo. Digging the '80s style.