Go here, download the ISO version of memtest86+
("Download - Pre-Compiled Bootable ISO (.zip)")
http://www.memtest.org/
Burn a CD with the ISO file, using CD burner software and a
burner. The ISO is tiny, so the burn should only take a
couple minutes to complete. The CD will be bootable.
Install the CD and boot from the CD.
When booted, the screen will look similar to this. 640x480 mode,
with a blue background.
http://www.memtest.org/pics/i875-big.gif
In this state, the test would run forever, or until you stop it.
Quitting the program will cause the computer to reboot, and you
might want to remove the CD if you don't intend to boot from the
CD at that point.
The program has a pass counter, and a couple complete passes should be enough.
For a decent amount of memory, it could take a couple hours for the
test to run. For a laptop, you'd probably want to be plugged in while
running this. It uses a fair amount of power, so the fan will
probably be running.
If there are any errors, they will be printed in the lower section of
the screen. You want "no errors", to consider this test to have passed.
If you have a severe error problem, the screen might even begin to
scroll, so you cannot see an image like the one shown above.
This test is not perfect. If you pass it, it does not mean your
computer is trouble free. Memtest86+ is good at detecting "stuck"
memory bits, but perhaps a bit less good at transient problems.
But if your memory is really messed up, you'll find out pretty quick.
If there are enough errors, it could even mess up the appearance
of the screen, or memtest86+ could crash.
A second test, is to run Prime95 from mersenne.org . That is a program
which searches for prime numbers (a math thing). But, the program has
one nice testing feature. In the menu for the program, you can find
a "Torture Test" option. The program carries out a math calculation
where the answer is known, and if the answer is wrong, the program will
stop and tell you there was an error. For a machine that is not stable,
the "Torture Test" will stop in 30 seconds or less. If the machine is
healthy, you should easily be able to run it for four hours or more.
(If offered an option, the "blended" test is good.)
Prime95 has an option to "join" the search for prime numbers, but you
do not have to join to use the torture test option.
Prime95 also draws a lot of power when it runs, the fan will be running
probably constantly, and the laptop will get hot. Make sure it has
adequate ventilation during the test, as it could overheat, depending
on how clean the vents on the cooling system are.
If the video on the laptop is built-in to the chipset, the video uses
"shared memory". Thus, colored squares could be caused by the system
memory that the video is using, becoming corrupted. On the other hand,
more expensive laptops have a separate GPU and video memory chips.
That gives higher performance. If you get colored squares there,
then the separate video memory chips soldered next to the GPU could
be defective. In some cases, the separate GPU can be unplugged and
replaced, which might be cheaper than replacing the whole motherboard.
On intermediate priced laptops, there is sometimes a separate GPU, but
it is soldered right to the motherboard, in which case the colored
squares problem means a new motherboard.
So, try the memtest86+ program and if it passes, then try Prime95
(Windows version, if you are using Windows) and see if the computer
still passes that. Changing out the memory, and trying some other sticks,
is what you'd do as a potential debugging step. In some cases, the
problem could be on the motherboard of the laptop, such as if the
low voltage regulator powering the processor or memory is defective,
and making less voltage than normal. That tends to reduce the stability
of whatever it powers.
Heat is always a problem with laptops, and more so when the vents get
clogged.
HTH,
Paul
