Are you asking about installing QTP, or installing the license server to manage your 7 concurrent licenses?
Per HP, installing the license server software (Sentinel LMS) on a virtual machine is technically unsupported.
We have QTP v11 installed on both physical and virtual systems and have found no significant problems with either. The nice thing about the VMs is they can be more easily restored/rebuilt than physical machines.
(Opinions and information contained in this post are wholly my own and do not reflect the opinions of my employer.)
As Trudy mentioned, it's easy to access & manage VM's. But the performance of QTP on VMs is not at it's best compared to physical machines. There are memory issues when running length/large number of tests on a Virtual Machine.