<<Even on your Windows drive, I think you'll find that GRUB is installed in a directory named /boot.>>
My Windows drive (hda1) is an ntfs partition. I'm not at that computer to check right now, but I hope you aren't saying that the Ubuntu install created a directory and wrote files to that partition? If so, I guess I know even less than I thought about how linux installs work. That sounds really dangerous.
<<So, when you select Ubuntu from your start-up GRUB menu, it's going and loading GRUB from your slave drive, and giving you options that include your Ubuntu system and also Windows, right?>>
That's what I believe it's doing. I thought grub's menu.lst itself was read from the slave drive (in /boot) each time, but it sounds like you are saying the slave drive wouldn't have to be present for the grub menu to function.. I have some reading to do. Thanks for your help. As long as I know that if one drive fails or is removed, I can still boot the OS from the other, I'm happy.