Re: Drivers etc... (oh, the pain)
There was a mixed bag when it came to software modems. I actually found that I could get mwave modems working relatively well in Thinkpads around the same time as you had trouble. Admittedly at the time, Redhat 7 and 8 (not RHEL) did not have the mwave driver in their repositories, but it was available, and built relatively easily on mainstream Linux distros, and worked quite well.
I did have an HP Riptide sound/modem card combination card that was more troublesome, and I completely gave up on that, both for sound and modem.
I've not tried to get integrated modems in laptops working recently. It's all a bit pointless since 3G dongles and public/guest WiFi are so common.