This driver actually camr from Dell support, and was listed as supporting the Crystal 4236b/4611 chips.
The Dell file was an executable that created 3 floppy disks containing the drivers. This file is a self extracting archive of those drivers.
Extract to a directory of your choice and activate setup.exe; uninstall any previous versions if necessary, then select 'install driver'.
You will be prompted to restart immediately. After rebooting windows will detect the hardware and ask for the 3 installation disks: simply point it to the driver directory when it does.
I've tried a few of the other drivers for the 4236 chip but none worked, despite installing correctly.
This one did :)
Hope it helps.