Amazon.com officially opened its Android Appstore on Tuesday. The store offers thousands of free and paid software applications for tablet computers and smartphones running Google’s Android operating system.

However, Apple Inc issued a trademark complaint against the largest online retailer in United States. Apple decided that the name of Amazon’s online application store is just too similar with their App Store.

The Amazon Appstore offers features that challenge Google’s own Android Market. It allows users to test applications that they are interested with a simulated Android phone. The simulated phone can be accessed through the computer using a mouse. Amazon calls it the “Test Drive.”

The company, in collaboration with Rovio Mobile, also offers another perk to its users through their Appstore. The Angry Birds Rio for Android will be launched exclusively at their Appstore. This allows customers to download the app for free, but only for a limited time. Amazon will also launch ad-free versions exclusively for Angry Birds and Angry Birds Seasons.

In 2008, Apple made an application to register the name “App Store” as a trademark in the United States. It has even attracted legal challenge from Microsoft Inc. Today, the application is still under consideration at the Patent and Trademark Office.

Apple wanted Amazon to stop using the name. It said consumers might be confused whether Amazon’s application store is approved or sponsored by Apple.

Amazon software developers will get 70 percent of the sales. However, the company will set the prices for each application. There are about 3,800 applications available in the site now. It can be downloaded through a mobile app or through the web interface.

Currently, Amazon Appstore is only available in the United States.

The Microsoft Corporation had just recently completed their Windows 7 Phone software. This new software will be formally launched to the public on October 11. By November, Windows 7 is expected to be installed on several handsets that are believed to compete with Apple and Google Android smartphones.

Samsung and HTC Corp, as well as other groups of smartphones are expected to release Microsoft-based phones this coming holiday season.

The employees of Microsoft Corp gathered around last month at its Redmond, Washington campus. This marked the completion of their software and revealed how they really want to get themselves back in the fiercely competitive phone market.

However, it is still a question whether the Windows 7 is good enough to turn the iPhone obsolete in the market.

According to Bryan Keane, analyst for the Alpine Mutual Funds that holds the shares of Microsoft, the product cannot just outrun everything that is out in the marketplace. However, Windows 7 might just be better than the other Windows platform.

Microsoft just missed a generation with their last phone operating system, Windows Mobile, admitted by Steve Ballmer, the Microsoft Chief Executive. The Windows Mobile struggled its way in the phone market while iPhone and Android reigned well with their touch screens and fresh applications.

Today, Microsoft ranks fourth in the fast-growing operating systems for the smartphone market in the U.S. It is behind Blackberry-maker Research in Motion Ltd, Apple and Google. From comScore research firm, Microsoft has a share of less than 12 percent.