A strange occurrence

[David A. Cobb]

 This isn't a development question, but I'm hoping the list's knowledge 
of GRUB will help me understand it.

Running Ubuntu 9.04, everything up-to-date, package "grub-pc" version 1.96+
GRUB-2 was installed after having GRUB 0.9x running for years.  The 
installation involved letting GRUB chainload GRUB-2 until I saw it was 
ready for primetime, then running an upgrade script.  I mention that 
because it's important to know that there is still a GRUB 0.9x image 
somewhere.

Trying to get past a nasty problem involving the interaction between a 
2003 Phoenix BIOS, and a big 160-GB disk that would not have been 
available in 2003.  I used BIOS setup to change the disk detection to 
manual, and made sure the numbers that came up were the same as after a 
successful boot.

Booted, and WHOA! I got the system-selection screen from GRUB 0.9x.  
But, it included versions of the kernel that were not installed until 
after I switched to GRUB-2.  Actually, the only thing I'm sure was 
"wrong" was the lack of a colorful splash image.  Well, no, actually, 
I'm fairly sure the console displays were not the same as the "WELCOME 
TO GRUB" that shows at the start of the GRUB-2 boot; but it goes past 
pretty quick, and I could be wrong about that.

So, maybe I hosed my GRUB-2 installation.  That wouldn't explain how a 
GRUB 0.9x image was found.  Anyway, I re-installed the package and 
(re)ran grub-install.  And rebooted.  And got the same screen.

So, eliminate the one variable I knew was changed: I reset the BIOS 
Setup to do automatic disk detection.  Voilla!!
I'm back with the GRUB-2 splash screen, and everything is cool.

But, I'm puzzled [yeah, that is my normal state].  Did the BIOS actually 
read a different image?  Or, did the "old" GRUB fail to chainload, even 
though there is no visible sign during a normal boot that the old GRUB 
is still around?  If the latter, should I consider writing the GRUB-2 
image onto the MBR again?  Or, would that be just asking for trouble?

TIA
--
David A. Cobb, computing t-rex.

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