Courier’s dead, but that doesn’t mean Microsoft’s done with tablets—Mary Jo Foley’s digging for more info on Menlo, a Microsoft project to replace Windows CE (inside Windows Phone) with a mobile version of Windows NT, like for tablets.

But wait, why would Microsoft want to replace the perfectly good Windows CE that’s inside of Windows Mobile, Windows Phone 7, Zune and lots more, with Windows NT, the core of its desktop Windows OSes? MJF is pretty sure Menlo is all about Microsoft’s future strategy in mobile, and the iPad might provide some clues as to the direction, in a perverse way. That is, MFJ supposes, if Microsoft ditched Windows CE for Windows NT, using the same kernel on like a desktop and a mobile device, Microsoft could have a “write once/run anywhere” thing going, where developers would simply have to change the interface to get their existing Windows desktop apps to run on a Menlo-based phone or tablet, giving them a huge application advantage out of the gate—the opposite of the iPad’s approach. (Not at all the same the thing as the HP Slate, we should note.)

Finally, MJF wonders out loud if Menlo is related to rumors of a Microsoft project called “LongARM,” porting desktop Windows to ARM—the same kind of mobile chips that powers basically ever smartphone on the planet, but are currently incompatible with Windowsm—which would fit well with what Menlo would be looking to accomplish.

The end result, if it worked, would be a kind of grand unification as a way to pursue Microsoft’s three screens and a cloud strategy, by having mobile devices running the same core as Windows.Which, while it sounds like a massive project (and headache), as we said when we put Courier to bed:

In fact, it makes sense for Microsoft to continue to trim away splinter versions of its core operating systems and focus on Windows 7 and Windows Phone 7 unity across all its devices. Hopefully some of the smart thinking we have seen in Courier will find its way into Microsoft’s tablets, whether they’re powered by Windows 7 or Windows Phone 7.

This would take that to the logical conclusion, with a single Windows core for every device. [ZDNet]