I too had the same problem after installing Red Hat. There is a lot of software out there that will try and fix the problem but if you're like me and just a newbie all this "rpm" and "emulation" stuff is a bit daunting. It was easier to just buy a cheap external modem.

Also, if some could tell me how to adjust the screen refresh rate under Red Hat I'd greatly appreciate it. Apparently it's done with Xvidtune but Ive found all this does is fit the screen to the size of the monitor.....splat