Black screen Crash HELP

[vulkan]

Hello,my rig is this
Ati radeon 5870 1gb,Intel 2600k 3.4ghz,2x4 gb Corsair Vengeance DDR3,Z68x-UD4-B3
So,as i was saying(i got that crash while writing this) i have a probelm since i built it(it is not software related as i have formated my hd once)
at random times(playing,serfing,booting) the screen may go black and i will hear all the fans running at maximum.
This problem can be solved after i restart(power off-on) or after several restarts(as it iwill apear of the restart so i have to restart again)
sometimes i will hear a continuos beeep signaling Gpu failure.
So my question is : is it gpu ,psu or ram?
this probelm may have been fixed(don't know for sure,maybe coincidence) by medling with the cables in the case-or pushing in the slot the gpu or the ram:/
Any ideas?

 

[vulkan]

edit:my PSu is thermaltake toughtpower 750W 5+yrs old

 

[Proximon]

Well, no. I mean it could be anything really.

How often does it crash?

I strongly recommend you review this list:
http://www.tomshardware.com/forum/261145-31-perform-steps-posting-boot-video-problems

 

[mouse24]

What fans go full speed? only the ones plugged into the PSU directly? Or only the ones plugged into the mobo directly? does that include the gpu fans? It could be heat related is what I'm trying to get at.

For now there are a lot of things it could be, gotta narrow 'em down somehow.

 

[vulkan]

The problem is that the crashes are Random,i may go with out them fora couple of months and then BOOM
More info to help you out help me : i hear no post sound when my pc boots(although i heard yesterday the continuous beep when it crashed)
And when i did the 6th month cleaning of the pc(plugged out gpu rams,change paste etc) i had this problem right away i would start the pc,i managed to solve it by pressing all the PSu calbes related to their corresponding cables(fan,mobo,etc)and generally making sure that everything was in the right place.....

 

[Proximon]

Did you go over the checklist? One of the items has to do with motherboard standoffs, for instance.

Maybe you need to carefully check things while the PC is running, perhaps you'll locate the bad connection.

 

[vulkan]

my thought was exactly that,a bad coonection or graphics card
i had in mind to replace my case as it doesn'r really faciliate me(bad airflow,liitle space,front hud sucks) i will also replace my psu with a corsair g650w.
i think that will solve the problem
nevertheless
please guys continue your brainstorming i REALLY appreciate the time you spend for solving my problem

 

[vulkan]

also do you have any idea aboyt why i do not hear any post sound??(although my pc works fine and i will hear a constant beep sometimes when i crash
(my screen went black because tribes ascend just loaded and my heart litteraly stopped for a second)

 

[vulkan]

any idea why i hear no post sound but i pc works fine?

 

[vulkan]

this problem is random,even if i try other psu etc etc i won't know what will fix it as now it runs smoothly...:/

 

[vulkan]

i searched in google and i found that mine are T2

 

[vulkan]

edit:in cpu-z it says that my ram is in T1...why?