Okay, installation is going. Thank you for helping with my newbie problem
One more question-- if I erased the partition Ubuntu was installed on, why did the computer reboot into GRUB? Does that mean that there are Ubuntu remnants that I should take action to get rid of?
Unlike with Windows, Grub is in installed in two locations: one at the start of the disk in a dodgy gap and the second part in the /boot directory. What happens when you delete your root partition depends on whether you have a separate /boot partition. If you do then Grub can load all its files but cannot find root so it drops to the Grub> prompt. If not, only the first part of Grub can run and it drops to a grub-rescue> prompt.
It would be a whole lot easier to manage if Grub were a standalone bootloader in its own partition. The way it works is that it is initmately connected to the linux OS that you last installed, typically.