Recently I went from 384 MB of ram to 512 on my laptop. It now shuts
down without warning. I'm pretty sure it's from over heating because
it's extremely hot after it shuts itself off. I've searched for a
solution but only found directions on how to replace the capacitors
which I'm leary of attempting. Please let me know what I can do. I'm
running XP home edition on a Sony Vaio.

I had the same problem with my laptop, my story is i bought a dell
inspiron second hand with no warranty, everything worked fine for 6
months then it would shut down without warning, i spent hours
searching the web for a soloution but i ended up finding the same
problem with other people , the problem was common household dust
being sucked into the heatsink and blocking the airflow for cooling,
to cut a long story short the best solution i came up with with help
from someone with the same problem was to dismantle my laptop, remove
the heatsink and blow the dust from it with and air blower.
This is only the solution too my problem, and i had step by step
instructions to dissmantle my laptop found on the web, and the problem
is fixed (for 6 mths at a time anyway)
I also downloaded a temp program called hdd temperature which is a
free download from CNET.com, all it does is monitor my hard drives
temp so i know when the next time to clean it is, i usually clean when
it gets to 62'C

Also there are cooling pads avaliable that you place under your laptop
and i think they are powered by USB, just type in "laptop cooling pad"
on a google search to find them and also "Sony Vaio overheating
problem" to find a lot of other people with the same problem as yours
and to see their soloutions.
cheers

Sometimes computers wont work with some brands of ram.  Are you sure
that ram is compatible with your laptop?  What's likely causing the
problem is that the added ram is too much for your laptop's power
supply.  So it overheats and turns off.

could be a number of problems, but i would try cleaning the ram
heatsinks out, and the psu units fans etc..... would then (to make
sure that there is no problem with the ramdevices) run memtest86
(based on linux available on a number of *nux boot discs although i
use a disc called ubuntu (good os))

A good troubleshooting process first involves eliminating any new
hardware or software that has recently been installed. Thus my first
suggestion is to remove the ram you installed, then test the system
and see if it still shuts down, also checking the manufactures website
and the web for similar problems could clue you in to any known issues
so you have a better idea what you're dealing with. If the problems
doesn't persist with the new memory out of the unit its likely an
issue with the memory you got, try either exhanging it for a new chip
or switch to a different brand of memory, I know that sony computers
in general, both desktops and laptops, can use largely proprietary
parts and thus you may also want to consider trying to get memory
through sony.

If the unit is still shutting down i'd look next into overheating
given the unit being very hot after shutting down, like someone else
suggested try blowing out the air vents on the unit with canned air or
some other type of high powered unit (like an air compressor). That
will sometimes help the problem and doesn't require taking the unit
apart at all, also a visual inspection to see if you can see any of
the internal fans could clue you in to a failed fan, which would have
a similar effect to a dusty unit.

Next I would look to getting the unit opened up to see if you can see
any more of the internal parts. If you're comfortable with computers,
while you have it open checking for dust and failed/failing fans, you
could also replace/re-apply some good thermal compound between the cpu
and heatsink/fan combo. Finally if that doesn't work I would probably
suggest taking it to a sony authorized repair dealer, and have them
take a look at it, one convient place within the United States is to a
Geek Squad agent located within any local Best Buy store.

Hope that helps!