Microsoft has said it hopes as many as 2 million people will try out Beta 2, its first widely-available test version of Vista. But it is also warning that installing Vista is not for everyone. Microsoft is not providing technical support for it and stressed that would-be installers should be "developers, IT professionals and technology experts." Moreover, users who upgrade to Vista now from Windows XP will not be able to roll back to XP by simply uninstalling Vista. Rather, they will have to reinstall Windows XP from scratch.

As for just how powerful your PC needs to be to run Vista, Microsoft answers that question by dividing computers into those that are "Premium Ready," "Vista-capable" or neither.

To be Vista-capable, PCs must have at least an 800-MHz processor and 512MB of RAM, along with a graphics processor that supports Microsoft's DirectX 9 rendering technology released in December 2002. But that's the bare minimum for running the operating system; PCs deemed Vista-capable are really incapable of running most of Vista's neatest features, particularly its new 3D Aero graphical user interface.

To run Aero, PCs must have at least a 1-GHz processor, 1GB of RAM and a DVD-ROM drive. That fits the description of most desktop computers sold in the past four to five years and most laptops sold in the past three or four. However, it's the graphics processor that may prove to be your computer's Achilles' Heel. It must have at least 128MB of memory and support not only DirectX 9, but also several more esoteric technologies such as a WDDM driver, Pixel Shader 2.0 and 32 bits per pixel.

Unless you're a gamer with a newish desktop PC, there is a good chance your graphics card is not Premium Ready. And if you have a laptop, not only are its graphics capabilities likely to lag even more, but it will also be that much more expensive to upgrade.