If you are experiencing failures when you perform P2V conversions using VMM you should create on the source computers boot drive a file called scvmm_enable_winpe_tracing.txt. The source computer is the computer that you are trying to convert to a virtual machine. Once done you will need to run the P2V conversion again. During the new P2V conversion VMM will create a new file called: scvmm_winpe.etl.
This file should have all the information needed to troubleshoot a failed P2V conversion.