Using Microsoft's new Windows Phone interface feels at times like placing a small frame on wide landscape, and then moving it around to get a sense for the larger picture. People accustomed to self-contained mobile screens will find this jarring at first. For example, as noted in one early review, "PowerPoint" looks like "PowerPoir" because the text trails off the edge, until the user swipes to see the rest.

You can see the effect above, in one of the promotional images Microsoft is using to illustrate the concept. It's almost as if Microsoft designed the Windows Phone software for something larger, and then figured out a way to make it work on smaller screens. What if that's actually what the company did? How would this look on a slate?

Pretty cool, as it turns out.

Just to be clear, the images above and below are nothing more than crude mockups that I put together by modifying Microsoft's own images to show how well-suited the Windows Phone interface would be for slate-style machines. I'm making a distinction between the underlying operating system and the on-screen interface because Microsoft CEO Steve Ballmer made a point of telling financial analysts last week that the company would be offering Windows 7, not the Windows Phone operating system, for slates.

I think Ballmer is telling the literal truth. But that doesn't mean we won't see something very much like the Windows Phone interface on slates.

Here's the thinking on this: Pretty much everyone agrees that the generic Windows 7 interface just isn't well-suited for slates. Mary Jo Foley of ZDNet.com's All About Microsoft blog discussed this topic on the TechFlash podcast this week, and after thinking about it I agree that Ballmer was being a bit coy in his comments.

This is still in the realm of theory and speculation, but the most logical conclusion is that Microsoft would offer a special version of Windows 7 that can boot up directly into a Windows Phone-style interface.

Even the name is easy to predict: "Windows 7 Slate Edition."

As Peter Bright of Ars Technica notes, there is a precedent for this at Microsoft, in the form of the Windows Media Center interface for large living-room screens. The comparison makes sense because Windows Media Center is sold as a premium product -- originally debuting in its own high-end edition, now built into premium Windows versions. Microsoft would be in a position to market the hypothetical Windows 7 Slate Edition in the same way.

Which means that its profits would be protected and potentially enhanced, not jeopardized as they would be if the company were to offer a mobile phone OS on devices it has long categorized as PCs.

Microsoft will defend its choice of Windows 7 for slates in part by asserting that people want them to double as fully functioning computers. We got a preview of this message in Ballmer's remarks about slates during the meeting with analysts.

"I mean, let's not speculate, let's merely say when you get your Windows 7 machine, it will print," he said. "Let's just start with that. I mean some people actually like to print every now and then. Ours will print. I'm not trying to say that other guys aren't doing good work. I'm not saying that."

Ballmer's remarks related to the iPad during the Thursday meeting were interesting and colorful, but I thought this comment below was also very telling, as the Microsoft CEO was running through a list of the company's priorities.

"And then we get to probably the one that I think is most important -- it is the most important -- from a financial perspective, and that's Windows," he said. "You know, this was an amazing, amazing year. In the sense that Windows is our flagship product, Windows and Windows' success is a tide that floats all boats, so to speak."

That wasn't a surprise, of course. Instead it was a confirmation that the threats faced by the company in mobile devices and slates aren't causing to alter its fundamental approach. For now, at least, Microsoft is sticking to what has worked in the past, and trying protect the product that fuels its business.

Apple, of course, sees this market differently. The use of the iOS makes the iPad a cousin of the iPhone -- and its booming application ecosystem -- not a child of the Mac. Microsoft and Apple are in a wrestling match to define this space between phones and PCs, with each pushing for an outcome that plays to its own strengths.

With a Windows Slate interface, styled after the Windows Phone operating system, Microsoft would at least stand a chance. And if my theory holds true about the Windows Phone being a preview of Windows Slate, Microsoft is already preparing third-party developers for that future.

"Most apps will be developed as single page apps that span the width of multiple screens," wrote Benjamin Rubenstein on Neowin after attending a session on Windows Phone 7 "Metro" interface at the company's Mix 10 conference earlier this year. "To navigate the app, a user will pan side to side. ... Microsoft is pushing this as the preferred method for app development."

The big question in my mind would be the potential drag on system performance from running the special Windows Slate interface on top of a full-blown Windows 7 operating system. Making the Windows Phone operating system work on slates would seem more simple, efficient and user-friendly, and possibly faster to market.

Instead, Microsoft appears to be looking for underlying hardware improvements to support its plans. In his remarks, Ballmer was focused intently on the release next year of Intel's advanced "Oak Trail" processors, well-suited for slates. Microsoft and PC makers aren't waiting for Oak Trail to introduce new slates, Ballmer said, but he made it clear that the new processor is key to the long-term strategy.

"Oak Trail is designed to be lower power. Lower power is good in a lot of ways. It leads to longer battery life, no fan, lower kind of noise levels, a lot of less weight -- a lot of things that people like. And as focused as we are on this category, our partners are also focused in on delivering the systems and the chips that will enable kind of our architecture to continue and our software product to continue to move on."

It's crunch time. As Ballmer told his visitors from Wall Street, Apple has already sold more iPads than he'd like. Which means this will be another attempt by Microsoft to come from behind in a market Apple is defining.

Ballmer cited netbooks as a precedent. Microsoft was able to flip the bulk of the market back to Windows, and away from Linux. But as one analyst pointed out in a question, we're talking about Apple and Google here. Microsoft is running the risk of spending too much time marshaling its forces to protect its traditional business, at the potential expense of its long-term success in the slate market.

At the very least, it will be interesting to watch the company's strategy play out, whether or not it follows the theories presented here. In the meantime, here's hoping we get to try a real version of these mockups ... someday.