The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage. NEW YORK ( Trefis) -- Microsoft ( MSFT) launched Windows Phone 7 last year with the hopes of making a major splash in the smartphone market. However, the tech giant's biggest driver of value in smartphones so far comes from Android licensing fees as Android recently captured 50% market share worldwide and close to 40% market share in the U.S. market. The smartphone OS market is currently dominated by Google's ( GOOG) Android and Apple's ( AAPL) iOS that are both gaining market share at the expense of Research in Motion's ( RIMM) Blackberry and Nokia's ( NOK) Symbian. We currently have a $28 Trefis price estimate for Microsoft , which implies about a 15% upside to the current market price. Microsoft's Windows Phone 7 OS has failed to take off as successfully as it was planned while Android has rocketed. While the company expects sales to pick up with the launch of Windows Phone 7 Mango as well as the Microsoft-Nokia partnership, the second-quarter sales results for Windows Phone 7 were disappointing. However the company is licking its chops from the juicy licensing fees it gains from Android handsets. According to Horace Dediu, Microsoft sold around 1.4 million Windows Phone 7 in second quarter, which brought in around $21 million from the $15 per Windows Phone 7 that it earns. On the other hand, HTC sold 12 million Android smartphones in second quarter, and as it earns around $5 per Android phone from HTC patent licensing fees, Microsoft made around $60 million. This is three times the amount earned from its own OS from the licensing deal with HTC alone.