I have seen a bad NIC cause continuous reboots.

OK. its an onboard NIC. Bad Motherboard?

Run from a live cd for a while, if you do noy have the same problem that way, it
is likely either a bad hard drive or some important part of the filesystem that
is corrupt.

The last time I had random reboots it was bad memory. I found it with memtest86

I had the same problem with the built-in Intel graphics card and the older
variants of Knoppix. Strange graphics and then rebooting. I tried some other
Linux distros some time ago, I cannot remember which and the results were
automatic reboots. Windows NT also causes automatic reboot. The major Linux
distros (Ubuntu, Suse, Fedora, Mandriva and their derivatives), the new versions
of CentOS, Mepis, Knoppix, Sabayon are not a problem for this PC. 2000, XP,
Vista and 7 are not a problem either. 98 installs fine but then, "your VGA card
is not supported" or something like this, 95 installs fine but then it says
there is not enough memory.
So your problem could be compatibility with some components.

If you think it may be heat related, lm-sensors and the computer temperature
monitor applet will show you what is happening. Both require some setup, Google
will take you to detailed instructions.

Random re-boots are the worst problem to fix and are usually hardware
related but trying a Live CD or even ASUS GATE ( which is a built-in
Linux Kernel in the BIOS ) will verify this as they will fall over as
well.

Fixing is a different matter and you've already started with the PSU
and CPU HSF but look at RAM and also cables ( I've known SATA cables
to go faulty just as much as IDE ones !! ) so start pulling things off
the board. Don't overlook the CPU itself - again I've seen a bad
contact with the socket cause weird problems so try taking it out and
putting back in again.

Good Luck tracking this down - it's always a long job but work at it
methodically and you should get there :-)

PS - if *everything* has been tried without a fix then you are left
with a faulty motherboard. What's the warranty situation on it ??

The first thing I would try on a home made computer is checking the reset and
other switches to the main board. Make sure there are no intermittent problems
with the switches and maybe just try pulling the connector off for a try.

the problem has been solved. I
have no idea what was wrong but I re-socketed all of the items and its
working fine.

I just got done moving and the speed bumps may have jarred the memory
loose. Either way I think Im going to build a new one.

Knew somebody who emigrated to US from UK and the system case had to
go in the hold - packaged it well but during the flight the CPU HSF
was ripped from the CPU socket and trashed the motherboard / RAM due
to rolling around inside the case :-( Luckily had the sense to carry
the HD in personal baggage so not a total disaster !!

Moral of story - moving PC's needs care, and things can work loose

When I read Western Digital, alarms bells start ringing . Have a look at
your HD and if possible fit it in a different PC ,such that you can
eliminate HD problems as the cause of random rebooting if the HD is ' well
behaved '

Ive had great results with WD. Either way the problem has been solved. I
think it was the memory getting jarred loose. TY for the idea though. It
is old.