James,
Are you actually running kernel 2.4.18.bf2.4 ?? Try typing in uname -r at the command line. It must match exactly or the install will fail.I have tried the following command suggested by Gary Parker.# sh NVIDIA-Linux-x86-1.0-4349.run \ --kernel-include-path=/usr/src/kernel-headers-2.4.18-bf2.4/include/ \ --kernel-install-path=/lib/modules/2.4.18-bf2.4/kernel/drivers/video/
Also, you are using an older version of the installer, 1.0-5336 is the latest installer available at: http://www.nvidia.com/object/linux.html
If you compiled your own kernel, you will need to have the sources (still) installed in order to compile the nvidia kernel module (unless you made your own headers package...).
If you are running the testing or unstable debian distributions, there are several specific debian packages that can replace the Nvidia installer and IMHO are much easier to use. Do a search for nvidia ('apt-cache search' or www.apt-get.org).
Johnny.