Help ME Diagnose Random PC Crushes

[fantisjjj]

Hello

I 've been experiencing some random PC crushes for quite a long time and by "PC crushes" i refer to either
a)TOTAL crush- see some scrambled graphics at monitor , ALT-CTtL-DEL doesn't work etc either
b) PC reboots on its own and windows diagnostic tool cannot find a solution
* the a)total crush happens more occasionally than reboots

PC Specs:

• 
  O/S: Windows 7 64-bit Ultimate
  CPU: Intel Core i3-3220 @ 3.2Ghz (Stock Clockz)
  Motherboard: Asus P8H77-M LE
  RAM: Corsair Vengeance 8GB (2 x 4GB) DDR3
  PSU: LC power 650W active PFC
  VGA: Ati Radeon 5770 powercolor (Stock Clockz)
  HDD: WD Caviar Green 1TB

The whole thing started before like 4-5 months and its frequency is also kinda random (can happen from 1-2 times per day and then may disappear for 1-2 weeks)
The type of crushes i saw during the mentioned period are :

1. During gaming(nothing like FPS, always light games(like Dota 2) so extensive GPU stress is out of the question). Its always a "Total Crush" and most of the times, monitor shows a grey background with some white lines (in other words scrambled graphics)
2. While i finish watching to a streaming video (it rarely happens while watching a movie with a video software but 9/10 times happens when the streaming video stops). It also happened occasionally and not all the time
3. When I put my PC to sleep state it either "wakes" without hitting a button and sometimes reboots on its own, either i try to wake it up and sometimes it reboots after logging in windows.As the above issues that's also happens occasionally and not every time i put it in "sleep" state
4. Random and really RARE pc reboots while surfing (that always a reboot and not a total crush from what i recall)

What i tried till now is run windows memtest which didn't show anything wrong. Tried to stress CPU for ~30-40 mins, everything went ok including CPU temp which was max 42 Cel degrees.
Stressed GPU with furmark for ~15 mins. Everything seemed to be OK except the fact that its temp went to 80 C so i stopped it to avoid some dmg to the GPU

Plese gimme some ideas cause
Thanks in advance

 

[Vic 40]

My best guess and it can't be more than that is first the psu and than the gpu,but you probably have to swap those to see which one causes the troubles.

For a psu 650 watts seems a lot,but you have a lc power which just is a really bad brand.Buying another,if you have the budget,is an option,like the corsair builder cx 430watt.That one should already do and shouldn't be to expensive.

Your gpu is already an older one so maybe it has had it's best times,you could clean it and see if that helps. when it might be about temperatures.

Make sure that the ram is running at the correct timings and voltage in the bios.

Also make sure your motherboard has the latest bios.The problem with this is that you can't have a freeze during this so do an update with as few items attached as possible.
I mean with that with only one stick of ram and on the igp which means taking out the hd 5770 prior.
But that leaves still the psu which could be bad so i would first buy a decent psu.

About the bios,with the next program you could see which one is on your motherboard,
hwinfo32
open it and click run,in the system summary,which is the top window,you can find which bios on the right/middle side.You should have bios 0604 or later.Compare with the site of asus whether you have the right one.
http://www.asus.com/Motherboards/P8H77M_LE/#support

If you close the system summary and click sensors on the left top side you could keep a look at the temperatures of your gpu and the rest.