Microsoft has announced that it will close the application marketplace for Windows Mobile 6.x users on May 9, and is warning people to get their last updates in now.

"Applications and games acquired from the Windows Mobile 6.x Marketplace service installed on your Windows Mobile 6.x phone will continue to work after the service is discontinued on May 9, 2012," said Microsoft in a letter to customers. "However, additional downloads of these applications and games from the Windows Mobile 6.x Marketplace service will no longer be available."

Redmond also told users to back up their data as soon as possible, because if the phone loses any apps after the May cut-off data they won't be able to get them back. Microsoft isn't commenting further on how long it will continue to support the Mobile platform, but we're betting that announcement will come sooner rather than later.

The last build of Mobile, version 6.5.5, was released to manufacturers in October 2009, and even Steve Ballmer wasn't too impressed with it. He took personal charge of the Mobile team to kick it into shape, and the result is Phone 7.

The move is a not-so-subtle boot up the backside to those Windows Mobile users who haven't upgraded to a new Phone 7 handset. Since upgrading of software isn't possible in most cases, this could mean a slight uptick in Phone 7 unit sales – but one suspects that people who are still using the antiquated operating system are probably just using the device as a phone and aren't that bothered about apps. ®