Microsoft has recently released an update to extend its new hypervisor capabilities in managing CPU cores and virtual machines.
When released in June, the version of Hyper-V included as server role in Windows Server 2008, could manage no more than 16 logical processors and no more than 128 virtual machines per host.
The new software package, available as manual download and through Windows Update, allows Hyper-V to manage up to 24 physical CPU cores and up to 192 VMs per host (this last limit anyway needs a manual edit of the Windows Registry. Without it Hyper-V can manage only 150 VMs per host).