There isn't enough room in town for three separate versions of the Windows operating system, admitted Microsoft's Executive Vice President of Devices Julie Larson-Green.

"We have the Windows Phone OS. We have Windows RT and we have full Windows. We're not going to have three," she confirmed last week at a UBS Global Technology Conference.

Reading between the versions, Microsoft sounds as if it's looking for a unified, mobile-friendly edition of its operating system, while keeping the more intensive desktop version.

Two months ago, the company hinted at just that, suggesting Windows RT could make its way into phones.

'We should not have called it Windows'

Microsoft learned several valuable lessons from the ill-fated launch of Windows RT, and it paid heavily with a costly write-down of Surface RT tablets.

"I think we didn't explain that super-well. I think we didn't differentiate the devices well enough," Larson-Green surmised

"They looked similar. Using them is similar. It just didn't do everything that you expected Windows to do. So there's been a lot of talk about it should have been a rebranding."

She went as far as to say that Microsoft should have called it something other than "Windows."

"We should not have called it Windows. How should we have made it more differentiated? I think over time you'll see us continue to differentiate it more."

Whether or not the product of Windows Phone and Windows RT takes that rebranding route seems to be up in the air at the Redmond, Wash.-based company right now.

The new path

Toward the end of her comments, Larson-Green noted that Microsoft's path includes a more defined mobile operating system. One that's different from the tablets like the Surface Pro 2 running full Windows 8.1.

"We do think there's a world where there is a more mobile operating system that doesn't have the risks to battery life, or the risks to security," she said.

She complimented Apple's efforts in this area, saying "you look at iPad in particular, and it's a turnkey, closed system. It doesn't degrade over time.

"It doesn't get viruses. It's not as flexible, you can't do as much with it, but it's a more seamless experience, even though more simplified.

"It also comes at the cost of flexibility," she concluded. "So we believe in that vision and that direction and we're continuing down that path."

  • Read our ongoing Xbox One review, proving Microsoft got it right with its unified One console.