Virtual comm ports removal or reassignment?

I am trying to help afriend get his modem working (usrobotics9.2faxmodem) and his computer keeps assigning the modem to comm3, he now has 2 comm3's on his computer and the techs at us robotics say the modem is supposed to be atached to comm2 to work, can we get rid of comm3 or reassign it some how and get the modem working?
Any suggestions will be greatly appreshiated.
Andrew