Some new x64 systems boot from a GPT disk that contains an EFI or UEFI boot partition with an EFI BIOS. Traditionally this meant that the system was of Itanium architecture. SCVMM does not support P2V of Itanium systems as is documented in 'P2V: Requirements for Physical Source Computers'
http://technet.microsoft.com/en-us/library/cc917954.aspx. There are now x64 (non-Itanium) systems that boot with EFI. These conversions will fail as well due to EFI boot structure.
Simply check Disk Management on the source machine to see if the boot disk is GPT or MBR. If it is GPT, we do not support P2V as a GPT boot drive requires an EFI or UEFI BIOS.
This deals with a simple architecture incompatibility. Let’s assume a system uses an EFI or UEFI disk to boot. This also means it is a GPT disk. We are attempting to convert this to a virtual machine so that it can run on a virtual platform. Only Itanium and some newer servers with UEFI architecture can boot EFI as it requires a special BIOS. Hyper-V, and other virtualization platforms, cannot emulate this as they have a generic BIOS based on classic x86 and x64 systems. Therefore, the system disk must be an MBR type to boot in any Windows virtualization implementation. This requirement is not isolated to Hyper-V as any Windows installation cannot boot from GPT disks unless the processor architecture is Itanium or UEFI. During initial Windows installation boot disk type is detected, EFI or MBR, and the appropriate files and registry settings are written out to disk. Windows installations are thus tied to disk type.
There are no workarounds for moving a Windows system with an EFI partition to non-EFI architecture. EFI and Itanium are in lockstep. Classic x86 and x64 cannot boot EFI, and there and is no simple switch back to MBR boot.
EFI and Windows:
KB951985 - How to set up dynamic boot partition mirroring on GUID partition table (GPT) disks in Windows Server 2008
EFI/GPT not supported by P2V:
'The information below specifies Itanium systems, with the reason being that an EFI based system will not boot in Hyper-V.
The following restrictions apply to P2V operation system support:
VMM does not support P2V conversion for computers with Itanium architecture–based operating systems.'
EFI Support Information:
Extensible Firmware Interface Specification overview - Intel