Dell this week said that it has replaced over 15,000 Blackberry handsets in the company with Windows Phone devices. That should be a major win for Microsoft's struggling smart phone platform, but there's just one problem: Dell is using its own previous generation Windows Phone devices as it has thus far declined to release new versions based on Windows Phone 7.5.

Dell global CIO Robin Johnson told The Australian that while the company used to be "a major Blackberry shop," it has now replaced about 50 percent of its Blackberry devices with Windows Phones.

Using your own product seems to make sense. But after releasing the unique Dell Venue Pro last year--it's one of the few Windows Phone handsets to offer a portrait-mode, pull-out hardware keyboard--Dell has never updated or replaced the device. And since then, a whole new generation of Windows Phone handsets have emerged. Just not from Dell.

Dell CFO Brian Gladden first spoke of the plan in a Wall Street Journal interview last year. However, he said at the time that Dell would replace all of its then-25,000 Blackberries and the company had been working on the scheme for "several months." A year and a half later, roughly speaking, some 10,000 Dell employees are apparently clinging to their RIM devices.

RIM at the time called the Dell plan "a publicity stunt". "We find it highly unlikely that they will actually save any money with this move and far more likely they were looking for a little free publicity," RIM senior vice president of corporate marketing Mark Guibert said a year ago. "Consider all the hard and soft costs of purchasing, deploying and supporting new devices and new software inside a company."

More important, where the heck are Dell's second-generation Windows Phone handsets?