The Virtual Machine Manager feature that allowed you to convert existing physical computers into virtual machines through the physical-to-virtual (P2V) conversion process is no longer supported in System Center 2012 R2 Virtual Machine Manager and further
Microsoft states that it is aware of the need for P2V capabilities and essentially recommends to use a down-level version of VMM if this functionality is needed, for details see: http://bit.ly/17S2C4n

The V2V is also deprecated in VMM. The long term solution recommended by Microsoft is the use of Azure Site Recovery