Dumped at A:\ Prompt by KNOPPIX

[bfree]

I downloaded this file: KNOPPIX_V3.7-2004-12-08-EN.iso from a file sharing network

Ok then, first thing is to check the mk5sum of the file you downloaded, it should be a98fb9823414dc3d33c5e53f120c0339 It's possible you downloaded a fake or just a bad image (or the download is corrupt)

& burned it to a 800MB CD, using the boot-able option in Nero Express.

And it sounds like this is the real problem though, you should not have a bootable option! You should simply be buring the iso image to disk (burn/record image or something in menus).

I set CD drive D: as first boot option in the BIOS & restarted, all the hardware was detected, some of the screen messages were as follows:

Caldera DR-DOS 7.03
No FAT32 Volumes Found, exiting
Usage: ntfsread.exe
Partition C:\ installed

I then got dumped at this prompt: [DR-DOS] A:\>
After which nothing else happened, why didn't KNOPPIX run?.

You are not booting the cd at all, or if you are it is not Knoppix!