
Converting VHD Files To VHDX For Use With Windows 8 8.1 Server 2012 Server 2012R2 Hyper-V
You should use VHDX files in Hyper-V for the best performance! VHDX is a new format that is supported by Windows 8, Windows 8.1, Server 2012 and Server 2012R2 versions of Hyper-V. The main benefits of upgrading are:

Setting A Reliable Time Server For Your PDC Emulator
ISSUE
You need to set an authoritative time server on your PDC emulator and make it remain a reliable time source for your domain.