Introduction
It appears that OS X v10.2.8 modifies your Mac's firmware in a way that makes it impossible to boot YDL.
The fix
You need to upgrade to a new kernel. Log on to ftp.terrasoftsolutions.com/products/ydl, or a mirror and download the kernel to a shared partition. Then boot from your rescue CD, follow its instructions to get access to your root partition by typing:
chroot /mnt/sysimage
Then install the rpm on your CD by typing:
rpm -Uvh kernel-2.4.22-2c.rpm
where kernel-2.4.22-2c.rpm is the name of the kernel RPM you have found.
Make sure it is 2.4.22 or newer. You should have YDL back when you reboot.
This HOWTO was written by Troy Vitullo, Terra Soft Solutions
