Microsoft seized the opportunity on Monday at GSMA Mobile World Congress 2009 to unveil its new mobile operating system: the Windows Mobile 6.5.

The new OS was officially unveiled by the company’s CEO Steve Ballmer during his keynote. The Microsoft executive mentioned several new features and improvements of the new operating system such as an application store, a backup and restore service, and an enhanced mobile Web browser.

Windows Mobile 6.5 brings you a home screen with integrated view of your today screen, missed messages, and calendar appointments. The main menu is a very big list of applications and folders. Finding programs and other content on the phone is much easier and the main menu can be entirely configured by its users. The larger buttons, images and the rest of the graphics also make the OS more finger friendly.

The WM 6.5 also features My Phone, a service that lets users to back up their phone data to a password-protected Web service. Aside from contacts and text messages the My Phone service also allows users to upload videos from their phones.

Another useful and interesting feature of the new OS is the Windows Marketplace for Mobile. This is practically the main hub for searching, browsing, and purchasing mobile applications. Through it, users are able to download new applications over the air or from PC by entering the Windows Live ID.

The Internet Explorer Mobile that comes with WM 6.5 has more features. It is built on the Internet Explorer 6 engine, it supports Flash and JavaScript, it features zoom in and zoom out options and others.

The only bad news in this article is that, unfortunately, Microsoft plans to launch the Windows Mobile 6.5 in the second half of 2009.