I’m working with a system where I’m dual-booted between Windows 7 and Windows Server 2008 R2 on a VHD. Recently I booted to the VHD file (approximately 51 gb currently) and during the boot process it blue-screened when booting to the VHD. The blue screen indicated a lack of disk space condition but there was 30 gb of free space on the drive which stores the VHD file. To get the system to boot I freed up another 30 gb of additional space and after that the system would boot the VHD again.
Summary: Booting to VHD? Make sure that you keep some significant free space on the drive that has the VHD (approximately 50-60 gb or the size of the existing VHD file from what I’ve seen in my experiences).