Many thanks for your help!
Yes, I should have made this clearer. I don't have a USB CD/DVD drive for this laptop, so the only practical way to install Linux on its own HDD from a CD or DVD is by taking out the original Windows HDD, and putting in the Linux HDD as the main HDD.
What I want to do now is put the Windows HDD back in the main drive slot, and put the Linux HDD in the ThinkPad 2nd HDD adapter. With a little experimenting, I see that GRUB/Linux refers to the drive in the 2nd HDD as hdc (not hdb), so I've tried the following:
title SUSE 9.2 from 2nd HDD hd1
kernel (hd1,0)/vmlinuz root=/dev/hdc5 ...
Notice the hdc5 as the root. This starts the initial non-gui stage of booting going, but then it stops when it can't check the file system on hda5 (that's hda - the Windows disk). BTW, trying h0,0 instead of hd1,1 fails completely: Grub can't find anything to boot.
Anyway, this may or may not be possible, but if I could avoid buying a USB DVD (which would let me install directly to the second HDD), I like to be able to do so.