I guess its an old modem u have got there.I have one of these too.The problem is that the driver developement of these modems have been stopped by intel , cause they called them "archived" drivers.But still u can use them with the old drivers only and only if u have a kernel 2.4.* .It wount work on 2.6.*.
For 2.4.* goto intel.com and download the driver 1st.( you will have to put some effort to find it on the site).Then the installation is easy
Untar it,run the ./configure script , ad the make in the end.First identify the exact model of the modem then find the driver.