modem trouble

Hello.Newbie here so please be patient.
We need both our computers for our business but one cannot connect at all online.
Problem is:Under the general tab in dial-up isp properties window in the connect using space is:
red x with”Modem removed-unavailable device(com1).
I have tried making a new connection and have made numerous calls to isp.
Before this problem I was getting Error 50 and Error 31.
The problem computer is running win xp and modem is a soft v92 data fax modem with smartpc.When I run diagnostic check it says everything is ok and modem is on com 3.
Can anyone help with this problem?
Thanks so much.