Computer issues(overheating)

Now 2 days ago my computer started acting strange.
When i turn it of it starts loading and 10 secs after that i shutsdown.
I turn it on again the overheat alarm plays for 5 secs and its starts loading and turns off again.After 2 to 8 tries it manages to turn on.Then i runned everest and all the temperatures were normal CPU 40-42 deg C.The computer runs without lagging or what so ever.
video card 50

i turned on warcraft and started playing and after 3 hours non stop playing the processor was 50 deg C and the video card 62 but the computer was running with no problems.
I noticed that now my internet turns off for a sec and then comes back(never happened before using this internet for 3 years)

i cant find the settings in the bios but i remember that once i found it and it was set to turn of the computer when the processor reached 80 deg C

I cleaned the computer and still the same problem

I think its related to the thermal protection(its bugged)
Please i need some advice what to do

Intel Core 2 Duo E6300 1886Mhz 2mb
video card Nvidia GeForce 7300GS 256mb
Ram 2 sticks x1gb ddr2@333mhz

 

Do you have any fans in the case ? check the power supply.

 

i dont have any fans tomorrow i will get a fan for the video card
the power supply is ok nothings wrong fan is spinning
so is the processor fan

the computer is clean

its has been fine for 3 years now this is the forth the problem started 2 days ago

 

if you can install a case fan.Also take out the memory chips and reseat them.
It also could be the processor/ or fan going bad.

 

Damn its worse now.Before it started after a few tryes now it doesnt.I think its time to go to repair


i tryed removing the ram and nothing checked the fans all are working and blowing hard

And its not overhearing cause before when i managed to start it all temps are normal

 

Try disconnecting the power switch from the motherboards control panel and use a flat head screw driver to short the power switch pins on the motherboard. Also check for shorts, make sure the board isn't touching the back of the case and make sure eveything is seated correctly. I doubt your problem is due to heat.

 

the problem went away on its own just as mysterious as it came

 

check psu....if its old maybe that could be the problem