Hi! My laptop (HP pavilion zd8000) has lately been shutting down
suddenly without warning; the screen just goes blank and the computer
stops operating. Could this be from overheating (it's always seemed to
run hot)? If so, how can I prevent this, and are there any heat
monitor utilities you can recommend? Thanks!

Hi, I can't find any reports of anyone else having overheating
problems, so unless you have recently changed the hardware I doubt
this is your problem.

This problem may have been caused by Microsoft Vista Public Beta:
http://www.winsupersite.com/showcase/winvista_beta2_reliability.asp

How often does this occur?

Also do you use you laptop on your lap or on a desk, is the area well
ventilated? Does the fan appear to be working?

If you believe your computer is running hot, try a free utility called
Speedfan. (www.almico.com/speedfan.php) Install it and use the default
settings. The program will detect your chipset and typically will show
you the temperature of the various sensors on your computer. I would
say that on a laptop, over 60 degrees Celsius is pushing it. If that
is the case, you should look into getting a can of compressed air and
cleaning out your laptop vents (where the heatsink is; kind of looks
like metal fins).

To do this, hold the can of compressed air upright so that it does not
tilt and spill the liquid out of it. Flip the powered down laptop over
and locate the vents and shoot spurts of air into the vents to clean
them. Also locate the small fan(s) and gently lodge a toothpick in
between the fan blades to keep it from spinning and spurt air in to
clean the fan. If you don't keep the fan blades from spinning, the
gusts from the compressed air can possibly damage the bearings of the
fan.

Hope that helps out! Best of luck to you.

Oh I also forgot to mention, if heat is not the culprit, perhaps it is
a failing component in your laptop. Do you notice any irregular
behavior in addition to the spontaneous shut downs? If there is,
please mention them as it is easier to diagnose the problem if there
are more symptoms. Thanks.