Ok, there is other workaround for your case:
- convert machine without reconfig
- attach the system disk to other VM with Windows, load the registry in regedit and manipulate ControlSet in the following manner - delete ControlSet009, rename ControlSet015 to ControlSet009, change the value of Current to 9, detach registry, then detach disk. (The registry is located in \Windows\system32\config folder, if there is no SYSTEM hive there look at SYSTEM\CurentControlSet\Control\hivelist where the registry is placed)
- configure machine
That's all
HTH