Time is ticking for Microsoft (NASDAQ:MSFT). With the sales of mobile devices having already overtaken PCs, the total number of in-use Internet-connected mobile devices will overtake desktop computers some time this year, and Microsoft is still fumbling in the mobile arena. If the company can't get mobile right, investors will pay the price for Microsoft's missteps.

The days of desktop dominance are over
Microsoft has been the king of desktop productivity for decades. More than 1 billion people worldwide use its Office program, which made up 30% of the company's revenue in 2011. But PC demand is slowing, and in 2013 there will be more Internet-enabled mobile devices than desktop computers for the first time ever.

Here you can see the move to mobile, with projected global installed base units (the actual number of units in use) through 2015.

Source: KPCB data.

This has implications not just for traditional revenue streams for Microsoft, but also for the company overall. Microsoft sees the trend, just like everyone else does, and its Surface tablet and Windows Phone OS are trying to meet mobile head-on. But the problem for Microsoft is that its competitors are already there.

A code not easily broken
Microsoft may have dominated the desktop era, but its competitors are flying high in the mobile age. The company's decades of software experience aren't giving it a leg up in the mobile application world. Microsoft lags far behind Apple's (NASDAQ:AAPL) app ecosystem.

As of November, Apple boasted more than 700,000 apps in its App Store. The Google (NASDAQ:GOOGL) Play store followed behind with about 500,000 apps. Meanwhile, Microsoft stumbles along with just 150,000 apps in the Windows Phone store. To Microsoft's credit, though, the company has doubled the amount of apps since last year.

But the number of apps itself isn't as important as what the number represents: developers spending time with the platform. Here are what platforms developers want to make apps for, based on a recent Appcelorator/IDC survey of more than 5,000 developers. 


Source: Appcelerator / IDC Q3 2012 Mobile Developer Report.

Microsoft will have to convince developers that its Windows mobile platform is worth developing for. The best way Microsoft can do so is through strong Surface and Windows Phone sales.

So far, Windows Phone accounts for just 2.7% of all smartphones purchased in the past three months, and Microsoft CEO Steve Ballmer recently said that Surface sales have been "modest." So far, the combination of those two mobile pursuits isn't encouraging compared with Apple's and Google's dominance in the smartphone and tablet markets.

Adding it all up
When you look at Microsoft's offerings, things don't look too bad. The company's marketing the heck out of the new Surface tablet, and it's partnered with one of the largest smartphone makers in Nokia (NYSE:NOK) Last quarter, Nokia surprised investors by moving 4.4 million Lumias. Better yet, consumers seem to be taking to Windows Phone and Nokia. A recent Changewave survey showed customer satisfaction of Windows Phone topping Android, with Nokia's customer satisfaction edging out Samsung.

Recent evidence seems to confirm Microsoft has a strong offering in the mobile space that consumers are satisfied with once they purchase it. The problem is that Microsoft is fighting competitors that already reign over the mobile territory.

Fool contributor Chris Neiger has no position in any stocks mentioned. The Motley Fool recommends Apple and Google and owns shares of Apple, Google, and Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.