It doesn't seem to be possible to convert VHD files from Microsoft Virtual PC to VMC format from the same program. Simply not possible. You can only convert whole virtual machines into other formats, not just few files.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.