I've gotten ndiswrapper to work with some wireless cards, but I haven't yet suceeded with intel 3945 yet.
In Fedora 5, you have to have both the kernel and kernel-devel packages installed. Install them with rpm -Uhv packagename.rpm. Once both are installed, use ln -fs /usr/src/kernels/kernelname /lib/modules/kernelname/build. cd into the directory with ndiswrapper. tar zxvf ndiswrapper-version.tar.gz. cd into the new directory. Run make install. If there are no errors, cd into the directory containing the windows driver (inf file). Use ndiswrapper -i driver.inf. Use ndiswrapper -l. If it says hardware present, you've used the right one. Use modprobe ndiswrapper. cd into /etc. Use your favorite text editor to edit modprobe.conf. Add the line, alias wlan0 ndiswrapper to the top. Open the network manager and create a new wireless connection, you should see the ndiswrapper option. Unless I made an error somewhere above, it should work with most wireless cards.