Apple has iOS that powers tablets, phones, and MP3 players. Google has Android, which powers phones, tablets, and other consumer devices.
If Microsoft has a decent mobile OS, it's buried under so much marketing that I don't know what it is. I guess there is "Surface", but it seems pretty limited. I've never used it, much less seen it outside a commercial.
They need to come out with an OS, and brand it differently that "Windows". Windows makes me think big and clunky and slow.
Second, they need to stick with their products, and improve them until they get traction. Their approach seems to be make a few dozen consumer products, and drop the ones that don't immediately succeed - quantity versus quality. Why not pick the niche that helps your business the most, and stick with it. Phones, MP3 players, tablets, or some other technology - do it, and follow "kaizen" (http://en.wikipedia.org/wiki/Kaizen). Eventually your competitors make a misstep, and the ecosystem is yours for the taking. It takes a willingness to spend money, be stubborn, continuously improve, and wait till the big fish makes a mistake. Apple took out Blackberry, and Android/Samsung/HTC have grabbed a nice chunk of market share from Apple.
Microsoft is coasting on previous successes - Windows, Office, and more recently the XBox, and abandoning not-successes too quickly.