It appears that vcd to mdf conversion mainly represents attempts to convert old CD disk imagers from VCD format (VirtualDrive) to Alcohol 120% MDF format, something that can be done using several virtualization programs including those listed below.
Unless you also have additional metadata file for the MDF image (.mds, .mdi etc.) you may want to prefer a conversion to ISO format instead, because you will get much better support for your disk image.