virtualbox.org

Virtual Box 4.3.22 r98236. Base memory 4096mb, drive size 25gb.

Macbook Pro, Mid 2010, running OS X Yosemite, 10.10.2, 8 gigs RAM, 500gb drive, 90gb free.

Guest Operating system, Windows 8.1 Enterprise 64 bit.

I am not sure if I have to configure Virtual Box, it seems to automatically default to NAT and I can't find anything in the literature that says I have to do anything else to have it talk to the modem.

In Windows I am getting an error 651, "the modem(or other connecting device) has reported an error"

In the Virtual Box Network box it shows "attached to: NAT"

Thanks in advance for your assistance,
d.p.

Well, it is now working, but any insight would still be appreciated.
Cheers.

If you meant to install some drivers for your hardware modem in the guest or use it in any way, this wouldn't work. The VM is virtual ("V") and does not see host hardware.
You use other means to do so. But NAT is the default choice because it works out of the box regardless of what your host connection is. It makes standart calls for Internet which the host OS can directly use to run its own conneciton logic.