it is possible recompiling the kernel with kernel-source-2.4.20 (without xfs) with the standard debian method

with
cd /usr/src/kernel-source-2.4.20
make xconfig
load config file /boot/config-2-4-20-xfs
(make your changes)
save
make-kpkg kernel_image
...wait...
cd /usr/src (there is new 8mb files there)
instal l (2click) on kernel-image-2.4.20. deb

edit /etc/lilo.conf to point to your new /boot/kernel... and to your old /boot/kernel... in case somehing goes wrong
then

lilo -v (to save new lilo menu)

reboot