This Toshiba Satellite (and Portege) modem driver works perfect with Acer TravelMate 506T. It's actually the same modem.
Acer does not support Windows 2000 on TravelMate 506T, so don't waste your time with them.
For the sound driver just look for CL4299 on the Internet. It's easy to find. With the modem however, I spent hours to figure it out, that's why I'm uploading it here.