This HOWTO(http://www.cewindows.net/wce/linux-serial.htm) will tell you how to set up a masqueraded PPP connection via IrDA or serial port from a MS-Windows CE PC Companion to a Linux based notebook computer.
Please feel free to mail me if you have further information about the CASIO Cassiopeia.
Werner Heuser <wehe_at_tuxmobil.org>