it needs to sell 50 million smartphone in one year, thats half what nokia sell in a year, if u mean smartphone marketshare.

actually if u put the sales of android, iphone and windows mobile together u barely get to 20% worldwide.

if u mean total handset marketshare counting dumbphones, all iphones are not even 1% yearly.

Whatever numbers you're using must be pretty old. A year ago, Android iPhone WinMo was 25% of the world smartphone market. Today, the three make up 35% of the smartphone market:

http://www.bbc.co.uk/news/technology-10839034

As for the whole cell phone market including dumbphones, iPhones are closer to 3% of units:

http://www.gartner.com/it/page.jsp?id=1421013

But the real kicker is profit share. Nokia is just about the only company making money on dumbphones anymore, and they ain't making much. Smartphones are where all the money is nowadays.

For example, LG sold 30 million dumbphones last quarter (they don't have much in the way of smartphones, but you can bet they're working on 'em), earning a cell marketshare three times Apple's, and they ate a loss.

Puny Apple and RIM which only have 6% share between them devour two thirds of the profit in the handset market:

http://www.asymco.com/2010/08/17/androids-pursuit-of-the-biggest-losers/

This smartphone stuff moves fast. Zombie WinMo has kept a 5% share for MS thanks to carrier distribution and Windows brand-recognition alone. This time next year, Microsoft could easily have between 10-15% of the market.

Samsung also is currently busy pushing Bada OS in Wave and if this phone continue to fly from the shelves at current rates they might be not interested in W7 all that much.

But of course it won't stop them from having W7 phones in offer since they have every kind of phone there :)

Wow. 

How badly does Microsoft want a piece of this market? At least half a billion dollars badly:

http://techcrunch.com/2010/08/26/microsoft-half-billion-dollars-windows-phone-7/

On a visit earlier this month to the company’s headquarters in Redmond, Goldberg says company executives told him that Microsoft, along with its carrier and manufacturing partners, would likely spend “billions” of dollars in the first year for marketing and development. Another source familiar with Microsoft’s manufacturer and carrier agreements says the company will spend $1 billion on the launch, half on marketing and half on other development costs.

To put that into some kind of perspective, $500 million is the size of Apple's entire annual marketing budget for all products. I've only heard estimates of what WinPho7 will cost to license, but the numbers I've heard suggest it will take 40-100 million handset sales to pay for a billion-dollar launch.

thats not the problem people buy handsets, not O.S. other manufacturers are growing faster cuz they have smaller share, nokia is selling more smartphones each year, but recently being slow on releases due Meego OS project with intel  and symbian going open source on it's roots.

 microsoft needs over sell over 30m smartphones to get 20% marketshare, , and they won't, they have to outsell blackberry and people buy blackberry just for the messenger.

also android is getting traction hp announce may not be wm7 active, and rumors say dells probably gotta do the same and just released dell aero (android phone).

the problem with wm7 its lack of features like multitasking, meego/maemo(also have flash), iphone, android already have fancy UI, but they all have multitasking and phone features in place.

It will be a failure compared to the power of Android. 

Yes, it will take a lot to recoup that cost.  But there are several more avenues of revenue that WP7 will bring in than licensing.  Zune Pass subscriptions will likely see an uptick, app store purchases, and ad revenue are 3 of the big ones.