By Daniel Eran Dilger

Published: 06:37 PM EST (03:37 PM PST)

The president of Microsoft's Windows unit, Stephen Sinofsky, has again pointedly clarified that new ARM tablets running Windows 8 next year won't actually run existing Windows apps for PCs.

"We've been very clear since the very first CES demos and forward that the ARM product won't run any x86 applications," Sinofsky said in a meeting with financial analysts yesterday, according to a report by InformationWeek.

While the company has made no secret about the fact that it plans no cross processor support for ARM and x86 apps in Windows 8, some were confused by Sinofsky's comments at the recent BUILD conference, where he said that "the demos we are showing you today are equally at home on ARM or x86."

The hardware Microsoft demonstrated Windows 8 running on was primarily conventional x86 PCs, including an Intel Core i5 device made by Samsung that resembled the iPad. The company also showed the pre-beta software running on a prototype ARM tablet.

That device, powered by NVIDIA's quad core Kal-El ARM chip, was only briefly demonstrated to This is my next, with passing mention being able to "see" the Windows 8 desktop.

That doesn't translate into actually being able to run existing Windows apps or future Windows 8 apps compiled for x86 PCs, however. The only thing Windows 8 tablets will run are the web-based Metro apps.

Sinofsky went on to explain that adding cross platform support would be too difficult to support in Windows 8, saying, "If we allow the world of x86 application support like that, or based on what we call desktop apps in our start yesterday, then there are real challenges in some of the value proposition for [ARM] System on a Chip.

"Will battery life be as good, for example? Those applications aren't written to be really great in the face of limited battery constraints, which is a value proposition of the Metro-style apps."

Intel offers to disparage ARM tablets

Intel's senior VP Renee James had earlier remarked at the May Intel Developer Forum that Windows 8 on ARM would not support x86 apps.

"On ARM, there'll be the new experience, which is very specifically around the mobile experience, specifically around tablet and some limited clamshell [form factor products], with no legacy OS."

James added, "Our [ARM] competitors will not be running legacy applications. Not now, not ever."

Those comments were contradicted by Microsoft at the time, which claimed they were "factually inaccurate and misleading."

Microsoft not good at cross platform

As a company, Microsoft once tried to offer Windows NT with cross platform support for various processors, including x86, MIPS and PowerPC. That effort was abandoned starting with Windows 2000. The company similarly worked to support various mobile platforms in Windows CE but has since focused on ARM, the clear leader in that market.

With Windows XP, the company added support for both Intel's Itanium IA64 and the AMD-originated x64, a 64-bit extension of x86. However, both products require separate apps and separate versions of the operating system. In contrast, Apple has moved from 68k to PowerPC to Intel x86, each time offering robust backwards compatibility for existing apps.

In its move from x86 to 64-bit apps, Apple delivered a similarly smooth transition, allowing Universal Binary apps to work on either platform, and distribution one version of Mac OS X capable of running on either 32 or 64 bit hardware.

Apple's iOS is ARM-only, and iOS apps do not run on Mac OS X (and vice versa). However, Apple has never suggested that there would be one solution to run everything in the way that Microsoft has with Windows 8.

Users refuse to believe that Windows 8 tablets won't run Windows apps

Users commenting on stories about Windows 8 reveal that many people are under the impression that the new release, expected a year from now, will run existing Windows games, existing PC apps like Office and Photoshop, as well a new layer of Metro apps.

"Windows 8 tablets will have x86, 64, and ARM chips, so to say that Windows tablets won't run x86 code is just flat out stupid. The tablets handed out at BUILD are using Intel x86 chips, so to say 'the tablet doesn't support legacy apps' is idiotic," one confused reader fumed after InformationWeek cited the president of Windows at Microsoft as clearly stating "the ARM product won't run any x86 applications."

Microsoft is demonstrating expensive x86 tablets because those devices are the only ones currently capable of running the pre-beta demos. Microsoft has made it very clear that it expects tablets to run ARM processors, given the continuous failure of heavy, expensive, and far less efficient x86 tablets to find buyers in the market.

"So all this time Microsoft has just been making a touch tablet!" another user complained. "We all thought that they were going to make a tablet that would run legacy desktop apps. The wait is over. Go out and get an iPad."

A variety of enterprise users are already using legacy Windows apps on the iPad, via Citrix, along with other native iOS apps. Whether Microsoft can convince them to switch to Windows 8 remains to be seen. The company was unable to get PC users to switch from the iPod to the Zune, and equally unsuccessful at getting PC iPhone users to switch back to Windows Phone 7.