Assumptions:

1. Hard drive "B" is good. The external USB cable and associated computer USB output associated with hard drive "B" is good.
2. The problem could be hard drive "A", external USB cable "A", the computer, or the MVHD internal USB cable harness.

Do the following:

1. Disconnect the hard drive connected to internal USB "B" and set it aside.
2. Disconnect the other hard drive from internal USB "A" and connect it to internal USB "B".
3. If the hard drive is not found by the operating system, the hard drive is the problem. If the hard drive was found...
   
4. Disconnect the external USB cable between MHVD rear panel USB "B" and the computer and set this cable aside. The drive will disappear when you break this connection - this is expected.
5. Disconnect the remaining hard drive from the internal USB cable.
6. Disconnect the remaining external USB cable from the MVHD rear port "A" but do NOT disconnect it from the computer.
7. Connect the hard drive (either one may be used since both are known to be good) directly to the external USB cable formerly connected MVHD rear port "A".
8. If the hard drive is found by the computer this indicates the MVHD internal cable harness must be the problem (the computer USB port and the second external USB cable are good). If the hard drive is not found...
9. Disconnect the external USB cable from the computer and reconnect it to the USB port originally used by the first USB cable. If the hard drive is found, the other computer USB port is the problem. If the hard drive is not found, the problem is the external USB cable.