Microsoft, Palm and Verizon Wireless have scheduled a press conference for later today that is most likely to see the official unveiling of a Palm Treo smartphone running Windows Mobile.

The companies said that Microsoft chairman Bill Gates will join Palm chief executive Ed Colligan at the event.

The launch of a Treo phone running the mobile version of Windows has been rumoured ever since Palm One bought back the Palm naming rights from PalmSource in May. 

PalmSource develops the Palm OS operating system and was spun off from device maker Palm One in 2003. PalmSource was acquired by Access of Japan earlier this month. 

A Windows version of the device could increase the appeal of the Treo with enterprise customers who are demanding close integration with existing Windows systems.

Palm is a long time supporter of the Palm OS, and this conversion to Windows would validate Microsoft as a maker of software for mobile devices, according to Michael Gartenberg, research director at analyst firm Jupiter Research.

"This event, if it actually happens, would mark a powerful turning point for Microsoft, more from a psychological perspective than a market share perspective, but that's the key to getting momentum going for the longer haul," he said.