Hi
Before anybody is going to be able to help you, you need to reveal something about your modem like Internal or External? Whether or not it is a WinModem ( a software modem ) whwther or not "other device" actually has been assigned a /dev such as /dev/tty0 or something. You may not even have to install a driver since it sounds like your kernel has already picked it up. It just may need to be configured and IIRC Mandrake has a some kind of "Internet-Start Here" that walks you through inserting an initialization string, etc. Again, iirc, it has a built in diag that will let you know if it's "talking". There is much more you can do right from command line but not w/o some more info. You might also poke around your modules.conf ( or conf.modules as some RH based distros like Mandrake call them ) with a text editor to see if any reference to a serial device is in there. Gather some info, play around, and write back
Jimmy