HELP to diagnose issue!!

matrat

Hi all,
I built a PC about 4 years ago now and started acting up on me last night so hoping someone can help me find a way to identify the issue rather than having to buy multiple new components. 
Here is the components;
Intel Core i7 3770K S1155
32GB 4x8GB Corsair CMZ32GX3M4X1600C10
120GB CSSD-F120GB3A Force 3 
CORS 850W CP-9020043-UK PSU
Asus P8Z77-V PRO Z77 MoBo 
2GB MSI HD7850 OC PCI-E
1TB WD10EARX SATA3 HDD
So what happened is during a normal operation of updating my media library, no real load, the computer died. It started itself up, turned off again and then the boot screen came up saying that the overclocking failed. The mobo had configured the overclock so i went into bios, set it to normal rather than extreme and machine booted up fine. Worked for an hour or so and then during a file copy to an ext HD, the machine died again, however this time no picture would come at all.
I tried moving the HDMI to the mobo port, no difference. 
I then opened machine and removed video card completely and still no help.
I then noticed that the DRAM-LED light on so i disconnected all power and re-seated the RAM and checked all power connections.
Next time it fired up the DRAM-LED flashed and goes out correctly, but now the BOOT_DEVICE_LED is on.
I think i ruled out the following;
I disconnected both the SSD & HHD and tried to boot in various forms of one or the other connected and no better.
Checked PSU and provided a constant 11.9 and 5 volts. 
Removed the mobo battery for 10 min and no difference. 
Tried using the jumper cap, didnt work, tried jumping without battery, also didnt work. 
I left the machine then late last night with the battery out and will try it again this evening but im pretty confident that given the overclocking failure from before that it wont solve anything. 
So by my logic i have it narrowed down a failure in one or more of the following;
Mobo
CPU
RAM

I dont have access to another board, ram or cpu so does anyone know of a way i can test any or each of the elements to know they are not the cause?

Thanks in advance

jhud

Ok you can try using 1 stick of ram as you have 4 i recommend testing with each one so only one in machine each test. You may fine one is faulty or more then one.

Maybe memtest86 run to see if there are issues.

jhud

http://www.tomshardware.co.uk/forum/311177-30-asus-overclock-failed

Found this its pointed out faulty motherboard seems to be same issue

Senecio

One of the simple things that I would try is to remove the CPU heat sink fan, clean up the surfaces and reapply new thermal paste. These symptoms sounds similar to a previous experience of mine of over heating.

matrat

Thanks for the input folks.
Just to update, got home and removed the cooler and cleaned off the thermal paste. Put the battery back in and same issue.
Then tried all 4 sticks in the first ram slot individually and no better.

Think all i can do at this stage is ring local computer shops tomorrow and hopefully they have a machine there to test cpu, ram and psu and will leave it def a mobo issue.

Thanks again for help and if anyone has any other ideas how to test any of the components myself then i would appreciate it!!