Palm, Microsoft and Verizon have launched the Windows-based Treo smart phone in San Francisco today.

The Windows-based Treo 700w has been expected for a while now, especially since Palm separated from PalmSource, the company that develops the Palm OS. Analysts and enthusiasts have been speculating that Palm would eventually turn to a different operating system vendor for its PDAs and smart phones.

According to Gartner, Microsoft has made steady progress with its mobile operating system, and handheld vendors actually shipped more Windows Mobile-powered devices during the last quarter than Palm OS-based devices.

Sam Bhavnani, senior analyst, Current Analysis, said that, Microsoft's ability to link Windows Mobile to its enterprise software, such as Exchange, makes perfect sense for Palm, which has been trying to break into the corporate market for a long time.

The Treo, a PDA that can also make voice calls, is one of the hottest selling mobile devices on the market, he added.

Todd Kort, principal analyst, Gartner, said that, Palm and PalmSource had hoped to use Cobalt, the code name for a smart phone version of Palm OS, in an upcoming Treo, but it never came to pass.

Palm then used Garnet, an older version of the Palm OS, in the Treo 650, and did a significant amount of development to make Garnet suitable for a phone.

Although the Treos have enjoyed a good run in recent months, Motorola has signaled its intentions to challenge Palm with the Motorola Q, a Treo-like device that will run Windows Mobile 5.0 when it is released early next year.

The other major operating system choice on the mobile smart phone landscape is made by Symbian, which is partly owned by phone giant Nokia.