error 15 in grub on second HD

I installed Ubuntu 6.1 on a second HD (the first has XP) and Grub on it (hd1,0). Grub appears when I boot through the second HD, but choosing any OS causes an "error 15: file not found" to show. The following are the initial lines on it, as it appears when I boot:

root (hd1,0)
kernel /boot/vmlinuz-2.6.17-10-generic root=/dev/hdb1 ro quiet splash
initrd /boot/initrd.img-2.6.17-10-generic

I notice that when I change the first one, I get another error, so it should be right that way. I guess the second line is where the problem resides, as Grub doesn't seem to be finding things on their places. Through WinXP I can see that the kernel file on its place ( at /boot/), as well as the initrd file. I am relatively new to Linux, so I'm having problems trying to figure out what to do. I tried to check things on the HD through the Ubuntu LiveCD, but it doesn't give me access to those, therefore it doesn't look like I can modify any installed files. I tried several ways to install Ubuntu through the LiveCD, but only the one with the root (/) and swap partitions worked, and not always it went through (most of the times it would keep saying the root partition hadn't been chosen, no matter what -- I saw several people complaining of this also).

In summary, my system has partitions hda1 and hda2 with XP, and hdb1 (root) and hdb5 (swap) -- I couldn't figure out why the #5 -- with Ubuntu; I kept the original MBR on the HD1, the Grub boot manager was put on the second HD.

If there's no easy way out of this, I wonder if there's a way to make a boot CD in order to boot into the installed Ubuntu (not the LiveCD).

I'd appreciate any help with this.