I don't know if the last answer helped your or not so heres the way I did it...
Put in your installation disc/diskette get into rescue mode and make a note of where it mounts your system image. It was /mnt/sysimage in RHWS.
Change your root to your system image
chroot /mnt/sysimage
Then look in your /lib/modules directory
cd /lib/modules/
ls
This is your kernel version so make a note of it.
then you can do a mkbootdisk (not specifying a device so it defaults to fd0 I believe)
mkbootdisk your.kernel.from-last-step
At this point you should have a boot disk.
From one newbie to another, good luck.