Microsoft got into virtualization when it bought Virtual PC in 2003. After VMware made its entry-level products free earlier this year, Microsoft followed suit, making Virtual PC 2004 free for all.

While Virtual PC 2004 doesn't run on Vista or support Vista virtual machines, Virtual PC 2007, currently in beta, does. Detailed on downloading VPC 2007 and setting up Vista in a virtual machine are at Microsoft's Vista blog.

Virtual PC 2007 blends the capabilities of the products mentioned above. Like VMware Player, VPC 2007 can run on 32- and 64-bit PCs, though it can only create 32-bit virtual machines at the moment. Like Parallels, Virtual PC uses Intel's and AMD's chip virtualization for faster performance. And while Virtual PC can support a wide range of guest operating systems, it can itself only be installed on PCs running Windows as the base operating system, not Linux.

One similarity between all three products is their inability to support 3-D accelerated graphics. That means you won't be able to test Vista's Aero graphical user interface or play the latest first-person shooter video games. In general, virtualized interfaces tend to look rougher and "paint" more slowly than nonvirtualized ones.

Getting your hands on a test version of Vista