GPU won't boot past splash screen

So in the middle of a game a few nights ago, my PC suddenly froze and refused to respond in any way. After a few minutes I decided to power it off. Upon trying to boot up the system again, it displayed the Gigabyte logo, but soon after it displayed the 'No signal' error and did nothing else. After trying to boot up a few more times, I received a message saying 'Windows hasn't loaded correctly', and was given different options to try and repair my PC.

I have tried:
- Start-up Repair
- System Restore
- Reinstalling Windows 10
- Clearing CMOS
- Updating BIOS

So far, nothing has worked. The system does run when I disconnect my GPU and use my on-board graphics as an alternative, but the system seems to struggle (constant crashing & very slow). I know this problem is common with people installing new GPU's/ other hardware, but I've been using my setup for a few months now.

Specs:

Processor - Intel(R) Core(TM) i3-4150 CPU @ 3.5GHz GPU -
Nvidia GeForce GTX 460 SE
Motherboard - Gigabyte H81M S2PH rev 2.1
RAM - 1x 8GB
PSU: Corsair VS450
OS - Windows 10, 64-bit

If anyone could post a solution, that would be much appreciated, thanks.