With Apple (Nasdaq: AAPL) and Google (Nasdaq: GOOG) leading the shift toward mobile and cloud computing, some investors might conclude that Microsoft (Nasdaq: MSFT) will inevitably sink into irrelevancy. However, I can think of three reasons the company won't go the way of the dinosaurs, even if its longtime stronghold in PCs does.

1. Mango's ripe for picking
Windows Phone 7, codenamed "Mango," may have entered the smartphone market late and struggled to gain traction, but the operating system has generated a lot of buzz recently. Critics gushed over an early build of Mango back in July. Some of the bolder analysts have even predicted that Windows Phone will surpass iOS's market share by 2015.

Although I don't see Mango toppling the iPhone anytime soon, I do think it can bump Research In Motion (Nasdaq: RIMM) out of third place. A recent survey by NPD found that 11% of U.S. consumers planning to purchase a smartphone in the next six months are most interested in Windows Phone 7. Meanwhile, only 8% said they were interested in BlackBerrys. Additionally, 44% of those planning to purchase a smartphone in the next six months included Windows Phone 7 in their consideration, while 33% were considering BlackBerrys.

Over the next few months, we should see more interest in Mango, as the update hits existing handsets and new phones come on the market. AT&T just announced that it plans to add the HTC Titan, Samsung Focus S, and the budget priced Focus Flash to its lineup of Windows Phones this fall. Nokia (NYSE: NOK) will probably also invest heavily in marketing the platform when it releases its first Mango handsets in North America.

2. Someone built an ecosystem
It appears that Microsoft has taken a page from the Apple playbook, setting out to create a consistent user experience across all of its devices. Windows Phone 7, Windows 8's tablet-friendly "Metro" interface, and the next Xbox 360 dashboard update all have a similar design.

However, rather than copy the familiar grid of icons now found across the iEmpire, Microsoft has instead designed its interfaces around customizable live tiles, which users can set to launch an application, or display information and photos. It's an innovative design scheme that has the potential to do the impossible: make iOS look somewhat clunky.

The connection between Microsoft's platforms goes beyond just looks. They're becoming more tightly integrated as well. For example, Office365 -- the cloud-based version of the company's business and productivity tools -- will automatically sync documents edited on a Windows Phone with the user's computer, and allow users to collaborate in real time.

The company also plans to expand its Xbox Live platform to the PC and Windows Phone. I think this is an especially smart move. It reminds potential mobile gamers that Microsoft knows a thing or two about building a successful game library. I'm also hoping that placing Xbox Live on a PC will simplify the process of sharing media between my console and laptop. My current combination of the Zune Marketplace and Windows Media Extender works decently, but it could be cleaner.

3. Ooh, look at the clouds!
In addition to offering a cloud-based version of Office, Microsoft launched its own cloud hosting service, Azure. Since launching in February 2010, Azure service has signed up 31,000 subscribers and hosts 5,000 applications, but it has a lot of catching up to do. Salesforce.com (NYSE: CRM) and Google's App Engine both top 100,000 applications.

However, Microsoft has managed to snag a few big-name customers like Lockheed Martin, Xerox, and Travelocity. Also, tech news site The Register recently reported that Apple had selected Windows Azure and Amazon.com's (Nasdaq: AMZN) AWS to jointly host iCloud.

I also like Microsoft's strategy for bringing Azure to social gaming. The company has developed a toolkit for developing social games, which provides code and guidance for things like tracking achievements, keeping scores, and handling in-app purchases. Developers can download the kit for free ... as long as they host their finished games through Azure.

Foolish takeaway
Microsoft has put in place all the pieces it needs to survive the post-PC era. Now it needs to focus on execution. Azure should grow into a valuable asset, but if the company wants investors to see Mr. Softy as more than an old geezer again, Microsoft really needs Mango and Windows-powered tablets to succeed.

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