And then the potential buyer spies a Windows RT tablet across the aisle. It's a little smaller than the Acer. And it costs less. But when the buyer touches the display, the home screen looks the same as the one on the pricier Windows 8 system. There's even that desktop tile, the one that takes you to the Land of Windows Past.

What does the salesperson say?

That's not an easy question to answer, particularly for Microsoft. The company has a long-term goal of enabling ARM processor suppliers to compete with Intel and AMD in the Windows PC market. That's likely why there's a desktop tile on the Windows RT home screen. That's also why the UI plays so prominently in Windows 8.

So the company would like to give RT every chance to succeed. Fair enough. But as it dials in the positioning for the present, Microsoft had better not lose sight of the fact that neither RT nor the ARM players are ready to compete with x86 in the PC market. Otherwise, a lot of consumers who need new PCs may find themselves buying Windows RT tablets that don't do what they need.

And when they go to return the tablets, do you think they'll trust Microsoft enough to buy a Windows 8 PC? It's possible, I suppose.

More likely, they'll just go out and buy Macs.

Upgrading isn't the easy decision that Win 7 was. We take a close look at Server 2012, changes to mobility and security, and more in the new Here Comes Windows 8 issue of InformationWeek. Also in this issue: Why you should have the difficult conversations about the value of OS and PC upgrades before discussing Windows 8. (Free registration required.)