I would appreciate if you could help me out. I installed RH Linux 7.3 on Toshiba Satellite 1905-S303 laptop. Everything works fine except for modem. I can not get it to work no matter what.
Any suggestions would be greatly appreciate.

Build in modem - the conventional approach is that of a serial device

What kind of modem is it? Is it PC Card, USB, Serial?

according to my research, it is a amr winmodem.
http://thatitguy.com/?subj=qanda&tar...lite1905-howto
here is a how-to on linux installation for your laptop.
http://linmodems.technion.ac.il/pctel-linux/
here is the most recent copy of the driver....good luck.
as a last resort, always check
www.linuxonlaptops.com
they have a whole bunch of info on other ppl's experiences with linux laptop installs. if you get fed up, i personally can confirm that the linksys pcmlm56 modem/network card works great on linux. even works with the debian drivers (4 floppy set, notorious for not having drivers for PCMCIA card drivers that work).