Thanks for replying Alastair - I guess I just jumped the gun. The HDD was formatted, and the original HDD was full, but it took some time before it actually started using the second HD. I just checked today and it's used ~15% already.
Thanks again!
Sorry for bring up an old thread. After you install the second hard drive, is there something you need to do to make the NVR actually write to it? Its installed, but nothing is writing to the new disk. TIA