A couple of things jump out to me, and a suggestion.
First, you're mounting /dev/hda1 as your root partition, which if true,
you're then saying your kernel images are in the root directory. (They're
usually found in /boot) If, on the other hand, you're using a smaller
partition to boot from in /dev/hda1, then your root partition is incorrect,
but your image locations are correct.
One thing you can do to check this is to type the following command at the
silo prompt:
ls /
This will show you what's at the root of the current partition. You can
also do an ls on /boot as well to see if your image files are there. If
they're in /boot rather than /, you can boot into them as well. I think the
command is to simply type the path and name of the image you want to boot
with, followed by any options. For example:
/boot/vmlinuz-2.4.25.042904
Would boot the first image if its in /boot rather than /. Double check the
silo man pages for the correct format, I'm not sure if its completely
correct.
Other than that, at this point I don't know.