I'm trying to install Madwifi for my new WLAN card, a Netgear WAG511.

After downloading and installing the kernel source code, I tried to run the 'make' command. This gave me the next error:

Makefile.inc:91: *** KERNELCONF: /lib/modules/ does not exist..  Stop.
I figured I would need the Kernel Development Tools, but I can't seem to find them anywhere.
How do I solve the error or where can I download these Tools?