Longhorn Server will have a virtualization role that will basically replace the need to use Virtual Server when working with Longhorn. If you want to play around with the new virtualization role as of now, it is not going to be possible because this feature not present in any public betas.
If you are curious about what this "role" is and a little more information on how this will impact that way we run virtual machines, take a look at the following demo done byJeff Woolsey:
Video: Longhorn - Windows Server Virtualization
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If you are still a bit lost in terms of what virtualization is, check the Intel webcast below:
These videos introduce virtualization technology and point out the differences between sofware and hardware based virtualization. They explore existing and emerging usage models of Virtualization: Server consolidation, disaster recovery, development/testing, load balancing, fast provisioning, etc They introduce the next generation of Intel� Virtualization Technology (Intel� VT) and VT -d (Directed I/O) and suggest usage models for the future enterprise.