Thanks, dsullinger, but a funny thing happened on the way...
Both drives already had W2K installed. So with the smaller one (4 gb), I loaded SuSE, the dual boot came up fine. I could use either OS no problem.
Now confident, I dropped in the 18 gb, which of course has the working config, files, etc. Load SuSE, and all he** breaks loose. Just an error message, like GRUB Geom Error (not sure, I've since moved on). Could only boot Linux from CD, and could not figure out how to repair (I'm loading to learn, after all!). Finally abandoned all, losing months of work, reloaded Windows, then let Linux resize and load. This time different errors (one of which an absurd boot out of BIOS range - if it was out of bios range, I coldn't have put it there and anyway the drive was working fine with Windows alone).
So now I've given up. Notice SuSE 9.0 is for release this week. I'll order, then try to decide where to try it out - maybe secondary drive on desktop (with primary physically disconnected for safety). Well, I didn't expect this first step to be easy. General feeling is that Linux is almost - but not quite - for the desktop yet. These things take time.