I  extracted linux-source 2.6.18 and linked as /usr/src/linux
and extracted latest madwifi 0.9.3 
# cd madwifi-0.9.3/patches
#./install.sh /usr/src/linux 
# cd /usr/src/linux
# make clean
# make bzImage
# make modules 
# make modules_install  
# cp System.map /boot/System.map-2.6.18
# cp arch/i386/boot/bzImage /boot/vmlinuz-2.6.18

the system boots with this new kernel but i don't see any madwifi folder under /lib/modules

and 
#modprobe ath_pci gives error