I am no expert on these things, but afaik INITRD.GZ is some 'image' which is usefull, but not essential needed for your kernel to boot. I'f I recall this right (I guess google can get you more info) its needed for loading external kernel modules.

But - if there is a problem, you kan use a tool called "mkinitrd" to (re)generate an initrd.gz (or initrd-kernel-2.4.22-xfs.img) for your kernel.

this might help...

good luck

(and be sure to use google on this, i am sure that will help)