Virtual PC 2007 which has been in beta for while now, officially shipped today.

This release of Virtual PC 2007 introduces support for the following:

    * Windows Vista™ operating system as a host operating system
    * Windows Vista as a guest operating system
    * 64-bit host operating systems
    * Hardware-assisted virtualization
    * Network-based installation of a guest operating system
    * Running virtual machines on multiple monitors

Support has been removed for the use of linked disks in a virtual machine.