The guys have a Zoom mini modem on a used Pentium 450 Celeron which is currently running KNOPPIX, (We tend to use Knoppix Linux as initial boots as you can run it from the CD, perform diagnostics etc.)
I had the techs show me the instillation procedure, and sure enough it recognized the software modem and supplied a working Linux driver (make sure the modem is powered up at boot). Knoppix can be run from the CD or the Hard drive, however not one formatted for NTFS.
Usually we ONLY use OEM supported Linux software like Mandrake and now Lycoris, but apparently the version of Knoppix they are using is the most recent GPL, (Downloaded version.)
Generally speaking a software modem uses the host systems' CPU and this is designed to be managed by a Windows environment.
The bother you are going through will never pay the dividends a good modem will. Our P2 450 system with the installed software modem's benchmarks does not match the capabilities of most Intel P200 MMX with a USR 33.6 (hardware) modem and an Opera browser, that we produced 4 years ago. Granted a more modern CPU and mega memory will help but you are still banging your head against a wall trying to push mediocrity to just acceptable levels (Kinda' like Microsoft...)
I appreciate your dedication and we all like your troubleshooting efforts, but we feel your time could be much better spent. The
Linux customers we get seem to be a lot that appreciates performance not patch-work work-arounds and overtaxed system resources.
You might want to sell that modem and find a ringing deal on a 55.6 or 55.6 upgradeable USR hardware modem on eBay.