When you have Virtual Server or Virtual PC virtual machines, you can use them in Hyper-V. However, this requires quite some manual steps. For the minimum, you need to attach the virtual hard disk files (.vhd files) to the hard disk drives in Hyper-V. This requires at least creating a VM from the Hyper-V wizard, opening up the settings for the newly created VM and then configuring the drives (probably IDE) with the virtual hard disk files.
But there are more settings you may want from the original VM. Things like memory, CPU resource control, DVD image, floppy image, SCSI controllers, etc. If you do want those as well, you must open the VMC file in Notepad and make the adjustments in Hyper-V accordingly. When you have many VM's, this takes quite some time. I have done this for a server with 15 machines, all with different memory settings, multiple network adapters and multiple virtual hard disks.....
Because of the lack of VMC import functionality in Hyper-V, I have developed a "Virtual Server to Hyper-V import tool". This tool basically takes a VMC file and puts all supported (in Hyper-V that is) settings in the UI. From there, you can tweak the settings; update the virtual drive image paths, choose whether to create synthetic or legacy network adapters and more. Once you are done, you connect to a Hyper-V host and create the Hyper-V VM from the original VMC configuration (or whatever you modified) with one click.
I have used it with all my Virtual Server VM's and it worked very well.
I am working on a few remaining issues and hope to have those resolved soon.
Below is a screen shot of the tool.