H2O is right per usual. It's not a good idea to try a cheap FireWire to USB converter and I've never heard of a good result. There just not compatible formats.
Better options are to copy from the internal to CF or external firewire drive or install a FireWire card in your computer. If you've got a PCI-E slot, you can easily add a genuine firewire 400/800 card for $20-30 bucks. Older Macbooks will also have a firewire 400 port, but I would recommend buying one just to do transfer.
My view on the 744T internal harddrive is that it's nothing more than a backup and I often prefer to simply disable it. I will always transfer my files directly from the CF card would never want to transfer from the internal unless I absolutely had to. Firewire 400 is incredibly slow and ties up your device and computer. Copying files from the internal drive to the CF is also painfully slow, coupled with the fact that you're still going have to pull the data off the CF card again. Simply put, getting the data off the internal hdd is slow no matter what option you choose and for me, I don't necessarily need the redundancy and am confident the CF card will always work right. knock on wood.
dsnacks also points out a good thread about connection issues. I've heard of things getting fried when hot-swapped. Firewire is ancient technology and was always destined to be the first past-its-time feature on these units.