So far I've done this ten times. Only once was I actually able to boot to Debian. And sitting in front of my new Debian I spent several hours installing and configuring, which included deleting all the hundreds of Thai fonts (Why?), which ended with Synaptic deleting half the OS. It wouldn't run, nor would it reboot, so back to the drawing board.
This morning I followed some suggestions from a user on the Debian forums which ended with sudo update-grub. That command edited grub.cfg in the new Debian / folder as well as grub.cfg in the Xubuntu / folder, and now I no longer even get the (useless) menu; it just boots straight to Xubuntu. I'm ready for install number 11, but at the end where it sets up grub I need someone sitting behind me to tell me how, because it is clear that I do not know how.
