Sudden PC Shut-Down/Restart

First off, thank you very much for reading, and i really appreciate if you can help me with my problem! You are amazing!!

Yesterday and today i have been having problems with my PC restarting or shutting down.

Yesterday - 3 incidents
1) Screened turned black, pc restarted, froze when all the drives were loading (when its a black screen with white text showing all the ram, hard drives etc...) so i had to force shut down
2) Shut down completely (no sign of "windows is shutting down", just straight up black) and had to manually restart
3) Same as number 2, except it restarted by itself, and fans were still running

Today - So far to this post only 1 incident
1) Same as number 3 for yesterdays

Usually occurs during tasks such as browsing... nothing intensive.

I built my PC myself and it is 1 year old - Here is my build
-AMD PHENOM II X4 955
-MSI 870-G54 MOBO
-4GB 2X2 CORSAIR XMS3 1333MHZ
-500GB SAMSUNG SPINPOINT F3 250MB/S HDD
-500GB WD EXT HDD 7200 RPM
-XFX AMD RADON 6770 1GB GDDR5
-CORSAIR CX 430W PSU
-ARCTIC FREEZER PRO 7 REV 2 AMC

Arctic Freezer pro 7 installed a week ago, been fine before yesterday.

One problem, during installation, was that the ram was in the way of the heat-sink attachment fan so i had to slightly bend the ram away to fit the attach the fan.

Also the heat-sink doesn't fully cover the CPU. There is slight margin around the heat-sink that the CPU is exposed and not covered, mainly because the contact area of the heat-sink is not big enough. I am assuming this is normal though.


An Image of HW Monitor if it helps.

EDIT: I forgot to mention: The way my motherboard is built for AM3 the HS can either blow air to the GPU or up towards the PSU. There is no way possible to make it so that the HS blows air to the back fan. The way i have positioned it is so it blows air into the PSU.

Are those idle or load temperatures you listed?

These are idle temperatures while browsing on firefox.

Ooof. that's high for idle/browsing.

Thanks for the reply

Is it? I thought it was quite normal for a phenom 955 as they are naturally hot CPU's.

I had to replace my original heatsink as before it was around 55 - 58 degree C on idle! Absolutely mad! It was fine for the most of the year though, just suddenly went quite high :S

I think the installation of this heatsink was quite bad though. IT was so fiddely i had to move it around alot, kept sliding all over the place, eventually had to take it off and put the heatsink on in a different way so maybe a lot of air bubbles. But its a very hard Heatsink to put on!

Any Ideas on what to do for the sudden shut downs?