For business users who want Microsoft Office on their cell phones, Windows Mobile 6, the upcoming version of Redmond's mobile operating system to be unveiled next week, will be a must-have upgrade.

Mobile 6 comes with mobile versions of Outlook, Word, Excel and PowerPoint.

With the continuing increase in sales of smartphones at the expense of handheld devices, Office makes a lot of sense, especially for synchronizing with desktop files, according to Rob Enderle, principal at the Enderle Group.

Carriers and handset manufacturers who believe they can put the limited memory and storage to better use, however, are out of luck. Microsoft Office still comes with Mobile 6.

According to John Starkwether, a product manager in the Mobile and Embedded Devices Division at Microsoft, Office is part of the package. Starkwether conjectured that if a vendor really wants to exclude Office from the operating system, an accommodation might be possible.

Additional upgrades to the mobile OS include Microsoft's Direct Push Technology with automatic synchronization of Outlook calendars, tasks, and contacts using Exchange Server.

For security and management, Mobile 6 will also give mobile network managers the capability of remotely wiping out all data from a device should it be lost or stolen. Other security features include certificate options and storage card encryption.

Business users will also be pleased with the inclusion of mobile versions of the .Net Compact Framework and SQL Server in order to access a company's standard line of business applications remotely.

The Office applications are the most robust to date for the limited capacities of a cell phone. Spell checking in Word, though, is not included.

E-mail viewing will be easier on the eye with formatting, tables, and pictures viewable as originally generated.

One-click options for e-mail, such as "reply all", moving a message to a subfolder and "delete" have been added to accommodate the restricted functionality of a small device.

Windows Vista users on the desktop will be able to swap music, pictures, movies and Outlook information between the Vista PC and the mobile device.

Windows Live will integrate mail, messenger, search, contacts, and spaces.

Call history is now placed inside the individual contact card.

Enderle said that although there was "a lot of great stuff" in Mobile 6 Microsoft still has to focus on ease of use.

"Compared to the Apple iPhone with its simplified interface, Mobile 6 is still complex to use," Enderle said.

Devices with Windows Mobile 6 will ship worldwide in the second quarter.