Crashing tips?

[Matt Morgan]

I'm fishing for some ideas about where to start diagnosing a 
mostly-random crashing problem.

First off, let me say this is a 2.8Ghz hyperthreading pentium 4, 512 Mb 
of DDR400 ram, an Asus motherboard (not sure of the exact model), a WD 
80 gb drive, and a Sony CRX225 CD-RW. I have a 3COM 3C905b 100baseT 
network card (there's also an SiS adapter built-in that I don't use), 
and an ATI Radeon 9200SE video adapter. The sound built-in to the 
motherboard appears to be a SiS i810_audio.

This is a fairly new computer for me, I've had it maybe 10 days. I've 
only been a Fedora user for about a week more than that (temporarily 
used a different computer before getting this one). For a couple days 
after installing FC1 on this computer, it ran very well, except that I 
couldn't get XFree86 to deal properly with the video; it would only work 
on Generic VESA, not with the Radeon 9200 driver. Then I set up yum and 
turned on nightly updates; the next morning the computer froze, just 
after login, while KDE was starting up. During rebooting, kudzu found 
the video adapter and set it up for me. So now all the hardware is 
properly identified and working, and I thought, great! That's worth one 
measly crash.

Only the thing is, now it tends to crash a lot. Almost every day since, 
the computer is either frozen when I come to work in the morning, or 
freezes during KDE startup, just after I login. Then less often, it just 
freezes in the middle of working. For example, it froze when I tried to 
tell Firefox 0.8 to use gpdf instead of xpdf to open a pdf--just 
clicking on the "Other ..." button froze everything. Then this morning, 
it froze in the middle of typing an email message in Thunderbird 0.5.

I wanted to blame it on yum, thinking it didn't happen until I set up 
nightly yum updates. But it happens even during mornings that yum 
installed nothing overnight. So that seems like a red herring.

My primary goal in diagnosing this problem is not just to fix this one 
computer. I plan to switch my entire organization to linux over the next 
couple years, and I need to get a better idea of how to diagnose 
crashing on linux desktops. So my real question is: when your computer 
crashes, what tools, and what steps, do you use to diagnose the 
problem(s). You know, what log files, what common culprits, etc. Of 
course, if you have specific suggestions about how to fix this 
particular computer, I'm all ears for that, too.

Thanks a lot,
Matt