Recovering forensic data from a failed boot

[Joe Zeff]

As I may have mentioned before, my laptop runs F16 but will only boot 
properly from my last F14 kernel.  All attempts to boot from a 3.X 
kernel fail before gdm starts.  Are there any logs that survive after I 
reboot into the old 2.X kernel so that I can see just what's happening? 
  I presume that some of the data will be in /var/log/messages, but is 
there anything else?  Is there a way to be sure that a copy of boot.log 
is kept, or if it already is, where is it?  So far, just reporting on 
the error messages I see on the screen hasn't led to any suggestions how 
to correct whatever's wrong, so I'm hoping there's a way to get more data.