You might be able to look at lmsensors (if supported by your hardware) to 
check for temperatures.  Also SMART tools can report on drive health.  

If possible, remove as much hardware as possible, and see if it still reboots.   
Maybe even swap out some hardware with another PC to identify the 
component(s) causing the issue.

Jeremy

On Sunday 06 January 2008 9:40:03 am Jim Scott wrote:
> My Fedora 8 system (x86_64, kernel 2.6.23.9-85) started to spontaneously
> reboot this week. From what I've read, it's most likely a motherboard or
> power supply failure. Is there anything I can do with Fedora to help
> troubleshoot this?
>
> /var/log/messages doesn't seem to tell me anything useful. The last reboot
> came around 9:20.
>
> Jan  6 08:50:44 MainPC yum: Updated: mythtv-setup - 0.20.2-170.fc8.x86_64
> Jan  6 08:55:37 MainPC ntpd[2154]: synchronized to 216.14.98.234, stratum 2
> Jan  6 09:20:23 MainPC rsyslogd: [origin software="rsyslogd" swVersion="
> 1.19.11" x-pid="2015"][x-configInfo udpReception="No" udpPort="514"
> tcpReception="No" tcpPort="0"] restart
> Jan  6 09:20:23 MainPC kernel: rklogd 1.19.11, log source = /proc/kmsg
> started.
>
> Is there anything I can do to enable more logging of this issue? Here's my
> rsyslog.conf:
>
> # Log all kernel messages to the console.
> # Logging much else clutters up the screen.
> #kern.*                                                 /dev/console
>
> # Log anything (except mail) of level info or higher.
> # Don't log private authentication messages!
> *.info;mail.none;authpriv.none;cron.none                /var/log/messages
>
> # The authpriv file has restricted access.
> authpriv.*                                              /var/log/secure
>
> # Log all the mail messages in one place.
> mail.*                                                  -/var/log/maillog
>
>
> # Log cron stuff
> cron.*                                                  /var/log/cron
>
> # Everybody gets emergency messages
> *.emerg                                                 *
>
> # Save news errors of level crit and higher in a special file.
> uucp,news.crit                                          /var/log/spooler
>
> # Save boot messages also to boot.log
> local7.*                                                /var/log/boot.log