Random BSOD's, and and random grey screens

Hi,
My PC is giving random BSOD's, there is not set pattern. Once I got a BSOD while playing NFS Rivals and then while surfing via firefox.

Not only this: I am getting random grey screens, where PC monitor will go completely grey and PC will stop responding , task manager wont open. So ulimately I have restart via button on the CPU.
Yesterday, I left my PC turned on overnigh for some downlaoding stuff, I woke up in the morning to found that it hung up at the night giving a grey screen.

Just now I was plauing FIFA14 and monitor again suddenly went grey and pc was not responding although music (media monkey) was playing in the background, but pc wasnt responding, so i have to restart it.

And on other occasion I got a BSOD on the login screen

EDIT: Please check the second post too.

Hi, I just had a BSOD again. I have attached some screenshot of the error and also uploaded the new system and dump files.
Please check :)
Attachment 312036

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Attachment 312037

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Attachment 312038

Code:

Host Name:                 OM
OS Name:                   Microsoft Windows 7 Ultimate 
OS Version:                6.1.7601 Service Pack 1 Build 7601
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Standalone Workstation
OS Build Type:             Multiprocessor Free
Registered Owner:          Abhisheak
Registered Organization:   
Product ID:                00426-OEM-8992662-00400

Counterfeit installations such as yours contains heavily modified code that causes the installation to behave it unexpected ways. Analysing BSOD's and determining their causes on these sorts of installations is very unreliable. For this reason, many analysts won't attempt it.

My recommendation is to install a genuine version of Windows. This will minimise the problems you are experiencing, and make subsequent diagnosis of BSOD's far more reliable. Once you are running a genuine Windows installation, and are still experiencing BSOD's, we will be happy to help you solve them :)