Quoting from TG Daily:
Following up on this morning’s news of six versions of Windows Vista, Microsoft’s next-generation client operating system, a Microsoft spokesperson told TG Daily this afternoon that Virtual PC Express, a feature of Microsoft’s new Enterprise and Ultimate versions, will be designed to run older editions of Windows as a subsystem.
“Virtual PC Express will be able to run any previous version of the Windows operating system,” the spokesperson wrote. “Customers who have annuity agreements with Microsoft automatically are granted a second license to install Windows as well as downgrade rights. This enables a customer to install an older version of Windows on top of Virtual PC Express without having to acquire an additional license.”…
Read the whole article at source.