OT?? Refusal to boot from external USB

[BeartoothHOS]

	My #3 PC is a handed-down Dell PowerEdge sc1420, now running F11, 
which began life as a server for a list I help manage. (The list is now 
hosted elsewhere.) I call it BBB (Big Black Beast), since it's so much 
larger and blacker than any of my others.

	I also have a Lite-On external USB DVD-RW drive, which the BBB 
sees perfectly well when it's plugged into it. I can read the files on 
it, which look normal afaict -- in fact, I have installed F12 on two 
other machines from the same DVD.

	And I have the boot sequence in the BIOS set to start with the 
DVD drive, in order to upgrade to F12 that way. But it doesn't. 

	I'm pretty sure I've installed Fedora releases on BBB before, 
using the DVD drive (certainly the first one, when the it first came to 
me).

	I have previously tried "preupgrade" on the BBB several times; 
the grub screen now shows an F11 kernel, then the preupgrade option, then 
more F11 kernels. When Anaconda starts at all, it's because I've clicked 
that second (Constantine) option -- and then it hits the dread lack of 
space, and aborts.

	Afaict, Anaconda never gets launched from the DVD.

	What am I doing wrong? Do I just need to get the Constantine 
option out of there? 

	If so, is it enough to edit /boot/grub/grub.conf? Or do I have to 
find and dig out everything it refers to? Or what??
-- 
Beartooth Staffwright, Neo-Redneck Not Quite Clueless Power User
I have precious (very precious!) little idea where up is.