You are sending faxes out of ACT! using FaxAdmin and you are receiving the outgoing faxes as well on your own fax machine.
This can occur if you are sharing the line with the outgoing faxes from Winfax Pro with an actual fax machine. This can cause your fax machine to pick up the outgoing fax and print out copies of the outgoing faxes. To resolve this issue, you must disconnect the physical fax machine from the phone line they share prior to sending faxes out of ACT!.