Well, it looks like Microsoft finally gets it. They removed the requirement for hardware-assisted virtualization (HAV) from Windows Virtual PC, which means that XP Mode can be used on more computers. Many computers do not support HAV at all and others simply do not provide a method to enable it in the BIOS. The fact that you can use XP Mode now without HAV, will enable the use of these older (and sometimes newer) machines with XP-compatible applications that do not work on Windows 7.
In order to get the support for non-HAV Windows Virtual PC, you will need to download and install Windows Virtual PC itself and then download and install the update that removes the requirement for HAV. Both can be found here at Microsoft's website.
