Sister, Son and I all have the same model Sony Desk Top Computer. Model VGC RB57GY. Computers are overheating and showing overheating error and shutting down. Mine now is shutting down after even a couple of minutes of being on, and have checked the temp and is not overheating. Seems like these computers have some type of glitch. Have taken to professional and he can't figure it out. Fans are all working fine. Problem is intermitent.

May I ask what Temperature you are referring to, and where you are looking for the temperature at/in?
In BIOS?
Do you have external software that reads these temps?

Motherboard temperature?
CPU (Processor) temperature?
ATI Radeon X300 graphics card GPU temperature?
(Graphics Processing Unit)

CPU temp:
What Processor is installed, and what is the maximum thermal limit for it?

Intel Pentium D Model 820.

http://ark.intel.com/Product.aspx?id=27512

64.1 degrees Centigrade, or 147.38 degrees Fahrenheit.

Checked the thermal paste to see if it has dried up?
Even if it hasn't, cleaning the bottom of the Heatsink, and the top of the Processor's case, and applying fresh, new, thermal paste is the way to go.
After a certain amount of time, thermal paste loses it's thermal conductive properties.

If it is a thermal pad, remove it, fly it out the window. They're junk.
Use fresh new thermal paste instead.
(Be sure to observe Anti-Static Precautions)

Fans are all working fine.
According to whom?
The tech?

Not doubting your abilities for one second. DO doubt the many 'techs' who profess so.

Computer case open, observe the Processor Fan. Ensure that is is spinning at all times, and not intermittently.
Also ensure that the fan is spinning at the correct RPM's.
(Revolutions Per Minute)

Same with the computer case fan's, Front and Rear.

Computer clean inside?
1) Processor fan?

2) Heatsink?

3) The area of the motherboard you can see with the computer case open?

4) The area Behind the motherboard, that you Cannot readily see, without removing the motherboard?

5) The ATI Radeon X300 graphics card?

6) The Heatsink on the Northbridge chipset?

Check the cable connection of the Processor fan to the motherboard, and the computer case fans, IF, they (Case fans), have three wires, AND are connected to the motherboard.

One wire is for Power
One wire is for Ground
One wire is for a sensor that detects when the fan should speed up.

Processor fan spin freely? Computer case fans? Feel like they/it, may have a bad bearing?

Let's diagnose together, and see if we can solve this.
If all of the above reads like a foreign language to you, I will explain step by step, and guide you.