randomly shutting down....motherboard problem?

My mom's gateway desktop's been randomly rebooting without ever being prompted to, and it's getting really annoying, because the thing would randomly start up at random times at night and stuff, and I talked to a guy in gateway tech support, and he seems to think it's a motherboard problem.

Symptoms:
-The computer starts, then promptly shuts down without ever being prompted to do so.
-Sometimes, the computer just shuts off randomly.
-The computer would randomly start up at random times.
-The 3 USB ports in the front of the computer are not operational. (all ports in the back are functional)
-It seems to work for a day or two after a thorough cleaning.

Theories:
-Software->disproved, hard drive was reimaged, it still has problems.
-Power supply failing->disproved, apparently the computer wouldn't start if its power supply was failing.
-Cooling system failling->Debatable.
-(new) Failling motherboard->Debatable.

Here's a transcript of the chat:

<quote>Incident in progress
You are in a Live Automation incident with ----------.
----------- joined the incident.
------------ says:
Thank you for contacting technical support. My name and badge number are ---------------. Please hold while I review your issue.
********** says:
hello? still there?
------------ says:
Hi *******
******** says:
hi
------------ says:
According to your submission, the serial number for your system is @#%$!@#%@#$! and this is a Gateway 550GR (desktop) computer. Am I right?
********* says:
yes
---------- says:
Thank you for verifying all the information. I see a lot of upgrade options (hardware/software) for your computer that will optimize and enhance it's performance and security. Let’s resolve all your issues first and then we'll discuss all those upgrades options later after we resolved your issue.
*********** says:
ok, but hold off on the upgrades for the moment
----------- says:
Okay I see. It appears that your computer is restarting am I right?
************ says:
over and over again, without EVER being prompted to
------------ says:
I see. It could be a bad motherboard
*********** says:
well that could be tantamount to replacing the whole computer right
********** says:
just curious was there some sort of recall i missed on this particular desktop?
------------ says:
We have a recall on battery for all notebooks as for desktops? We do not have a recall program
------------- says:
Replacing the motherboard will not cost you a new computer
********** says:
okay, but the motherboard holds the processor and all the chips and stuff
********** says:
isnt that the most expensive part in a computer anyways?
------------ says:
Yes that is right so you need to look for the same motherboard.
----------- says:
Motherboard is not too costly
********* says:
so it's not a power supply or cooling problem? i understand computers automatically shut down if they get too hot.......and a bad power supply could have the computer randomly shutting off
----------- says:
bad power supply will cause your computer not to boot
********** says:
so i guess it needs a motherboard replacement....would being in a dusty environment have something to do with it? or bad wiring perhaps?
********** says:
by the way the usb ports on the front of the computer don't work either
------------- says:
Then that should be the motherboard
*********** says:
okay well how much does a motherboard replacement usually go for? is it common for it to fail?
------------ says:
around $150-$200
******* says:
i see can you refer me to a couple gateway authorized service providers in the monterey, california area? (well other than best buy....they seem to have a pretty hard time figuring that out)
--------- says:
Try Circuit City, Office Depot and Fry's Electronics
********* says:
ok so i have this extended warranty thru best buy and they tell me that i can go to one of these other places and then get whatever it costs to fix it reimbursed....do you know anything about that?
------- says:
I have no idea about BestBuy's warranty
****** says:
ok well thanks for your help </quote>

Please help......this computer really needs to get fixed before I go away to college

thanks in advance.

 

I agree with the tech, it sounds like the MB. Based on all of the symptoms but most especially that the front usb ports are not working as they are directly soldered onto the board.

 

Buy other computer.

Seriously, pretty much all Gateways' are lemons these days (like my MX7515.)

Back to the topic, check the temp of CPU and other parts. If the temps go beyond 60'c, that may be overheating problem. But I think it is either power supply problem or MB. Just to know, even if PS is failing, but computer can start (like my last desktop with Silentmaxx one.) Try put PS which power output is higher than current one. If it still persist, that's the MB problem and you need to replace it.