After a little research, I found that Agere, the maker of my toshiba's softmodem, has beeen absorbed by LSI and that company has zero support for it.
Unless, someone knows what modem chipset is used on the A135-S4656.
After several days of searching, the only thing I've found out about the elusive Modem on High Definition Audio Bus is that Microsoft provided a hotfix for it, but that hotfix is not available for public download.
I even tried installing HP's version of it, but to no avail.
Installing the XP Modem drivers provided by Toshiba were also a waste of time.
From what I can tell, the Toshibas that have ATI chipsets do not have this problem.
I need help here.