Yes, and you can go both ways - from a boot from vhd image and to running in VPC or Hyper-V, or the other way. Sysprep would be required if you are going the other way, so that the minisetup runs to detect the various drivers when going from a VPC/HyperV vhd to a boot from vhd. This is to prevent the boot from vhd image from running the integration disk drivers when running on the real hardware.
An interesting utility recently released that you may want to check out is SysInternals Disk2vhd. It can do some hal fixups when going back to VPC:
It uses the volume shadow copy feature of Windows XP/2003 or later to create the image. I recently created a vhd from a ThinkPad T61P, and it started up fine on Hyper-V.