Modem not recoginised by Windows XP Pro

I had a Conexant Internal 56K modem installed which was recognised by XP as a Generic 56K Data Fax Modem on either COM 5 or COM6 port depending on the PCI slot I used.
I wanted to upgrade to a SwannSmart IIx 56K V92 Internal modem but XP refuses to recognise this modem on any of the PCI slots and when I try to install it using the “Add new hardware” or “Add” in the Phones/Modem section it installs the modem but only on COM 1 which is already being used. I tried adding extra COMM ports but there was a problem with the ports resources. As soon as I put the Conexant modem in, XP recognises it immediately. I have re-installed XP but this made no difference. How can I get XP to recognise the Swann modem.