PC keeps shutting down while playing a game

[Aerate]

Specifically Overwatch for some reason, but I'm sure it'll happen with any heavy game.

So yesterday I got a new GTX 550 Ti, while installing I decided to clean my CPU cooler as well, without knowing the thermal paste will dry up if I do that. I put back the cooler after cleaning without reapplying a new layer of thermal paste. Every time I tried to play Overwatch, 10 minutes later my PC powered down on its own.

Today I got new thermal paste and applied it on the CPU(pea sized dot in the centre), and am now getting 40-50C on idle and 60-80C when I play Overwatch. Yet my pc still keeps shutting down suddenly. I was even monitoring the temperature the last time it happened and this time it powered down even at 55C. It could've been that I didn't apply the thermal paste right, but the temperatures are stable enough imo so that might not be the case. If anything I can reapply it but I've heard you shouldn't do it more than once or twice so I want to avoid doing it. My GPU temperature is 75 C during Overwatch which sounds stable enough. But I'm still not sure what's causing it. My PSU is a Corsair 450W which is sufficient for the GPU and CPU.

Need some help please. My knowledge in this regard isn't complete so any assistance will be appreciated, thank you.

 

[harrysmellington]

What is the CPU?

 

[Snipergod87]

What was your old GPU?

 

[Aerate]

The CPU is an Intel i5 650 @3.2 GHz. Old GPU was an Nvidia 9400 GT. I clean installed the new drivers and uninstalled the drivers of the old ones so no worries about that.

 

[harrysmellington]

It could be possible that the temp reporting sensors are faulty. Install realtemp and run sensor test.
You will also need Prime95

Realtemp - https://www.techpowerup.com/realtemp/
Prime95 - https://www.mersenne.org/download/#download

 

[Aerate]

It could be possible that the temp reporting sensors are faulty. Install realtemp and run sensor test.
You will also need Prime95

Realtemp - https://www.techpowerup.com/realtemp/
Prime95 - https://www.mersenne.org/download/#download

Here are the results:

Last night it happened again so I decided to remove my additional hard drive and DVD writer to decrease my PSU load, so far it's good. But it usually happens after I use my system for long, I'm gonna keep my PC on for a while and try again, and update.

The only thing I'm mainly concerned about is if I should reapply my thermal paste or not. I don't really wanna ruin my CPU because of something really silly(albeit important).

 

[harrysmellington]

That's interesting, did load ever reach 100%? Also yeah reapply thermal paste just to be sure.

 

[Aerate]

No not at all.

And yeah I'll do that, thanks. Kept the PC on for a few hours and it didn't crash this time, although I did get frame drops on occasion. I guess it's safe to say it was my PSU in the end; 450W isn't much at all. I'll report if I get any problems again.

Once again thank you.

 

[harrysmellington]

No not at all.

And yeah I'll do that, thanks. Kept the PC on for a few hours and it didn't crash this time, although I did get frame drops on occasion. I guess it's safe to say it was my PSU in the end; 450W isn't much at all. I'll report if I get any problems again.

Once again thank you.

Did you run prime95? that should get 100% load. Try the sensor test again (in realtemp) after you reapply the thermal paste.