Claudia,
I am not up to snuff on Onebox although I did look at Updox at one time. I would think you could use Paperport on any computer. If Onebox is the system that allows you to receive faxes then I think you could use the Onebox file as a folder in Paperport. You just have to tell Paperport where to look for its folders. However, do not hold me to this as I have little-to-no expertise with Onebox. On another side, you could buy a Brother MFC with Paperport software included for what 10 months of subscription to Updox would cost you.
Leslie