In short, my computer froze twice in quick succession. Now it's not using my GPU and in Device Manager it has the error code 43, though it is powered up. I've used DDU to uninstall the drivers, installed new drivers, I've reinserted the GPU and the PSU cables, and tried the other PCIe socket. No change. Is it even worth going to a PC place and getting them to try the GPU? (One quote was £36.) Is it just screwed? The only notable coincidences are 1) for the past few days, first I got a BSOD, then my PC hasn't gone to desktop until it's started up everything, rather than normally going to desktop and then the antivirus etc. loading up after; 2) this all happened after I was out and my mum invaded and 'tidied' my room, so who knows if she bumped something or hoovered the outside or something. (Couldn't change the title of my last thread, and this is way more of an emergency. )
There's a good chance that you have a hardware problem. If I were in your shoes I'd back up and reinstall Windows from scratch. If a fresh install works then great, if not you have a physical issue to troubleshoot.
Reinstall from scratch rather than a repair install that keeps files? What would you say is the probability that works if a system restore and repair install doesn't? Because that's a huge thing to resort to that will usually end in failure and more misery!
Back up your install/partition with Clonezilla which will only save the actual used drive space [so long as it's not encrypted] and give it a go anyway. If the issue persists, you can just restore the partitions. Also, what GPU is it? Were you running any overclocking? It may just reached end of life sooner rather than later.
I'd be backing everything up on a few USB sticks if I can. If it solves the issue, then I will have messed about with my GPU, PSU, motherboard etc. for no reason. If it doesn't, I'll have done all that for no reason too, so either way there's wall bashing. I'll look that up. I saw about imaging too, but I've used most of my hard drive and waiting all day as it copies game folders and stuff seems very inefficient! It's a Zotac GTX 780 AMP! that I got from the marketplace forum here in 2014. No overclocking. The only other slight issues it had was one of the fans might get noisy if it was a cold dawn. Also recently it was shutting itself off at around 90C when there was no FPS limit, even though before that I had played a couple games with it off (by mistake, not regularly) and it didn't cut out, so that might be another change.
Alternative option is to source a cheap or even free "burner" second disk and install Windows on there. You may even already have one lying around. If your new installation works without issues then there's your answer. If not, pop the old disk back in and make a decision on how to proceed.
You can try a fresh install of windows on a spare HDD to see if it works. That way you can swap back to your old drive if it doesn't.
No spare hard drives, GPUs or other PCs to test on. I'm hopefully trying system restore, but the reason I'm hesitant to resort to buying a hard drive, reinstalling Windows etc is twofold: First, while it's been awesome at running everything at basically 'Ultra minus fancy shadows settings' at 1080 so far, I'm assuming when the likes of Cyberpunk and Star Citizen (ha!) come around, 3GB will be scraping the barrel and I might've upgraded anyway. Second, and why paying £36 to a computer shop would be silly, is that I could just sell mine as faulty for £20 and spend not far off £36 extra on a replacement 780 or 970, if not upgrade for more. (I guess I'm in the 'acceptance' phase of grief.)
Every time I have seen the Windows "error 43", it has been a dead or faulty GPU. It shutting itself off at 90C is a bit of a clue there I think.
Man, not even System Restore wants to play. Says it couldn't access a file, possibly because of an anti-virus, but I had turned off all of Avast's shields. I'll try doing it in safe mode, but after that I think I'll take the hint and let someone else have their fun with it. Thanks for everyone's help. Real shame I didn't have a spare PC lying around, that would've been too easy! Though the weird 'delay' going to desktop still remains from my other thread. I hope that's not indicative of anything.
Well I'm back a few hours later, and that system restore changed nothing about the GPU or the weird change in startup. Although I just realised - when I say the GPU doesn't work, it IS working because that's what the monitor's plugged into and I'm getting a picture. It's just in the screen resolution it says my monitor is some generic Plug & Play, and the resolution is down to a maximum of 1600 x 900 (I think it was). Woah that is super nice of you. Though seeing as I'm on Windows 7, the startup shenanigans, and that I'm petrified of messing about any further with the insides (let alone with disconnecting and reconnecting my hard drive), I'll just suck it up and upgrade. I hear Windows 10 is still free as long as you have the Windows 7 key.