MS/Linux, you'll probably have to use
to find out your modem's I/O port and IRQ (or you may find them out from Windows, for example).
But first, make sure your modem is not a winmodem (i.e. it is possible to make it work in Linux): www.linmodems.org
and TLDP's Linux Hardware Compatibility HOW-TO (www.tldp.org
to list your serial ports.
If the last one is ttyS3, for example, create a new one:
Then use setserial to set the port and IRQ:
setserial ttyS4 uart=<put your UART here, I don't remember it :D port=<put your port here, with 0x in front if it doesn't have it irq=<irq here>
(You can check out the UART of other ports, e.g.
will display you the UART (and many other things) about COM1.).
Then use pppconfig and it will detect your modem.