Computer crashes (?) when powering OFF

[pyrokov]

So i have this problem where my pc running seems to crash when i shut down my system. I click shut down, and it goes as normal. The 'shutting down' window displays with the windows logo, then it immediately crashes or something. My main monitor seems to turn to a random, single, faded colour. Often, the colour is black, but I've had teal and some other colours. My computer seems to be unresponsive, and doesn't turn off by itself even overnight, i have to manually shut it down.

I suspect that it might have something to do with my power supply because I've had a graphics card power problem on this rig when first purchased. On my third day of using the card, my video drivers would repeatedly crash, and eventually the system would crash with it. I solved this issue by setting my power option in the nvidia panel to "prefer maximum performance", I think it solved it because the card needed some extra power to properly run it, but when I shut down the system, perhaps the power setting had no longer applied to the card, causing the video to crash while the system shuts down.

Anyways, my specs are as follows

W7 Ultimate x64

i5-4690K @ stock

Gainward GTX970 phantom (factory overclocked, possibly causing the problem)

Gigabyte Z97M-D3H (BIOS ver F6)

Patriot Viper GREEN 16GB

840 EVO 240GB

EVGA SuperNOVA 750W

Thank you in advance

 

EDIT: Monitor colour actually isn't random, it's either black or blue. On rare occasions my pc shuts down without crashing. Also on rarer occasions my pc also has this black screen problem when i boot it on, the pc seems to just refuse to load, and i have to manually reboot.