OK, I think all of these good answers are telling me one thing: I need to do a lot more reading befire I can set this up properly.
Following earlier instructions I found when first adding Ubuntu to my Vista +Windows 7 setup, I have the Windows bootloader in primary control where I can select Vista (default), Windows 7, or Ubuntu (where the Grub loader takes over).
So now I see that Grub can't boot to Ext4 and LILO is better.
So I have a lot more to read.
Thanks to all who responded.