Permission errors are most likely happening when You are trying to do sometiong as user, that only root is allowed to do. Use a root shell (find itin the Knoppix menu) for ndiswrapper stuff. By the way, the exact error will be very helpful!

Reinstalling ndiswrapper:

version 1) You have an internet connection (maybe via LAN) - do as root:
apt-get update # this means updating the lists of available software packages
apt-get install ndiswrapper --reinstall # this one reinstalls/updates Your ndiswrapper software

version 2) Find another computer that has an internet connection, and search for an ndiswrapper debian package (.deb). Download it, and move it to Your target machine. There, You can install it using:
dpkg -i /path/to/Your/ndiswrapper.deb

Greetings

Update:
I think You'll need more Packages than just one. On my system, following ndiswrapper packages are installed:
ii ndiswrapper-common 1.15-1 Userspace utilities for ndiswrapper
ii ndiswrapper-modules-2.6.17 1.16-1 Linux kernel module for NdisWrapper for 2.6.17
ii ndiswrapper-utils 1.8-1 User space tools for ndiswrapper
ii ndiswrapper-utils-1.7 1.8-2 Userspace utilities for ndiswrapper
(You could check this out on Your machine with "dpkg -l | grep ndiswrapper")