Blinking underscore all of a sudden, need some help to get my workstation back up and running

[jarlenfos]

Hey guys,
I built my machine about 5 or so years ago now and it has been working perfectly as my main work machine all that time. Late last year I updated to High Sierra, I couldn't go any higher as my graphics card wasn't supported. That didn't bother me. Still working fine for the past year. Then earlier this week I got up to start work and turned on my machine and was greeted with a flashing underscore.

I updated my bios (already had the latest version but updated anyway to give it a fresh install) loaded optimised defaults then made the other required bios setting changes.

I created a bootable USB with high sierra with unibeast and was able to get to the clover options. I tried booting with safe mode and verbose mode. Safe mode did work once, but then the following 10 attempts to boot into safe mode using the -x flag didn't work, also nv_disabled=1 . I internally disconnected my extra drives and also tried booting with my graphics card removed. Same deal.

As a last resort I decided to try re install high sierra from the USB. I selected to install from the boot options menu and it greeted me with the apple logo and a progress bar, after 12h it didn't move past a white line.

I am running:
i7 4790
GA-Z97-D3H
GTX 750ti

I'm not really very knowledgable about this stuff and I'm not sure what to do here or where to go next.

Any help would be much appreciated.

 

[P1LGRIM]

also nv_disabled=1

nv_disabled=1 is meaningless, it should be nv_disable=1.

it greeted me with the apple logo and a progress bar, after 12h it didn't move past a white line.

Boot in verbose mode to show more information that may be useful for problem diagnosis.
Post a picture of the screen when it stops.