Access to modem com port help required

I use a BACS payment system which requires the modem to send the information. Since upgrading to Windows 2000 Professional I’m getting the message ‘error in communication initialization’ message which used to mean “switch the fax off to clear the com port” or even “the wrong com port is set for this software”.

I’ve checked all the obvious with the help of the BACS software helpline, disabled the fax using fax service management and checked it’s not running via Task Manager but still my BACS software (Hexagon V5) won’t work. Is there something else I should be doing to stop the Fax, which is just the one that comes with Win2000, from hogging the modem? It’s an ESS Data Voice Fax Modem.