I have a belkin wireless card on my pc that uses that same windows driver (bcmwl5.inf). You need to make sure you have the bcmwl5.sys file also, then ndiswrapper will work. I am a newbie at this but I was able to get this wireless connection humming.

1) I put both bcmwl5 files in my home directory.
2) Then I issued the command "ndiswrapper -i bcmwl5.inf" at a root prompt.
3) Then typed ndiswrapper -m
4) I then went to Kwifimanager and set up a config using my network name, my wep key under the Use encryption section, I then did a autodetect to see what my wireless setup was...mine was wlan0.
5) Then to get the dhcp working you have to enter the line in the script section "pump -i wlan0" or whatever your card setup is called.
6) After that I did an "Activate" on the same screen and wella my wireless connection came up.

Let me know if this works for you. I have a hard drive install of knoppix but this should not make any difference. If you can get this going I then can show you how to automatically connect at boot time. But first things first.