IF YOU HAVEN'T been stuck in a cave lately, you will undoubtedly have heard that Windows Vista SP2.1, aka Windows 7, will have an 'XP mode'. Before you jump up and down for joy, you should know that it won't do what you think it will, it is a scam.

Microsoft is conducting a very carefully crafted PR campaign to make Windows 7 seem less broken than the Broken OS (Vista / Me II), but it isn't. It gives long lead previews to people it knows will kiss up and not criticize the OS in order to create 'good buzz'. Sadly, with regard to Microsoft's Windows 7, the PC industry press is abdicating its responsibility to report objectively about a vendor's product, and the public is, well, dumb as rocks. It will believe almost anything it's told and never question the source. Yes, I am talking about you.

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Why is this important? Well, the main difference between AMD-V and VT is that AMD-V is able to virtualize memory access in a much more transparent way. When AMD-V based VMs look to memory, they take a few cycles hit, but VT VMs get hammered by having to do a bunch of translations on the memory addresses. The speed difference is quite extreme, and it is why AMD had a huge advantage in VMM deployments for several years. With Nehalem, Intel has caught up.

Neither however is able to virtualize peripherals, and the prospects of doing so are fairly dim. If either side puts that capability into the CPU and chipset, you will also have to wait for peripheral makers to get up to speed. On the high-end enterprise side, things like multi-port NICs will probably get there first, but consumer widgets won't see it for a long time.

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Windows 7 will grab the GPU to run the desktop, and it can't share the device. If it were even possible, you could possibly assign the GPU to XPM, but that would mean you'd lose GPU acceleration for the desktop, CPU use would spike, and things would start to resemble molasses in the winter very quickly. This much brain twisting logic is unlikely to be implemented even if it could somehow technically work. Basically, the host OS, Windows 7, can and must own the GPU fully.

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So, what you will get with XPM is not an XP machine but a bloated resource hog that emulates the worst of 2004. Slowly. It may be a good fit for green screen COBOL apps that won't run on the Broken OS, but that is about it, and you will pay for the 'privilege' in terms of resources used and speed of operation.

We won't get into the funniest parts (yet), but think about this, Microsoft is claiming that XPM will be able to interact with Windows 7 apps seamlessly. I don't doubt that it will be appear seamless to the user, but there will have to be some pretty horrendous low level OS contortions going on under the surface to make it work.

The news that people will not be able to run applications designed for XP on Windows 7 by tapping virtualization, as XP Mode supports, is discouraging for cash-strapped consumers and small businesses that hoped to upgrade without ditching existing hardware or upgrading their software.

Microsoft Corp.'s decision to give some Windows 7 users a tool to run Windows XP applications in a virtual machine may have been necessary to convince people to upgrade, but it could create support nightmares, analysts said today.

Windows 7 RC, slated for download by MSDN and TechNet subscribers today and by the general public on May 5, doesn't expire until June 1, 2010, 13 months from tomorrow, Microsoft confirmed today.

When asked why the company is giving users such a long free pass for the software, a spokeswoman declined to comment.

Microsoft Corp. plans to continue offering Windows XP to hardware vendors for use on netbook PCs for a year after the upcoming release of Windows 7.