I'm not sure what you mean by a "converter". If you have an SD card reader somewhere, then it's easy to swap PC36IMG.ZIP files in the root of the card.
If you don't, then you should name the HBOOT file to something else ending in ZIP and put it in the root, copy the ROM PC36IMG.ZIP to the root and reboot. It will start to load the ROM PC36IMG.ZIP file, just tell it No twice. Then manually load the HBOOT ZIP file and reboot.
If the phone keeps booting to the new HBOOT and you can't get to Recovery to restore a backed up ROM, then you'll need to say Yes to loading the Stock ROM.