So almost every session my PC randomly crashes playing this. Could be after 30 min to 3 hours I don't know. My screen just plainly goes black, I can hear the music for about 5 seconds then my PC crashes and I hear my PC beeping for some reason and it starts up again.

I've no idea what's going on, please help.

EDIT:

Forgot to mention my rig:

AMD FX 8350
EVGA GTX970 4GB SC
8GB RAM
Corsair CX 750M
M5A97 R2.0
Win8.1 64-Bit

Random crashes are the worst, because it's difficult to get to the cause. It could be a heat problem (CPU/GPU/PowerSupply), as the game is very demanding, but also insufficient power supply on full load is common (keep in mind, your graphics card needs at least a 500 Watt power supply) or any of the overclocking features could cause instability as well as your RAM module.

You could use stress test software to check for a general weakness. If the system crashes as well, the problem isn't game related and according to the stress test you might be able to spot the weak point.

Yeah the whole system crashes and reboots. Apparently it isn't just TW3, it just did the same thing while I was playing BF4 a minute ago. I'll look for a stress software and see where it goes wrong

EDIT: Ran a test with HeavyLoad and it didn't crash. CPU at 100%, ram fully used, spikes of 100% disk usage, and gpu load didnt even go higher than 10%. So I don't know what the heck is going here.

Crashes with Galaxy?
BF4 via Galaxy?

That's not much stress though. As the other components seem stable under 100% load, I'd investigate further into something GPU related. Check for alternative drivers or disable rather exotic graphic enhancements like ubersampling or the newest AA techniques. On high resolutions the positive visual effects are often rather minor anyway.

No via origin.
And I played some BF4 while using a monitor to keep an eye on my gpu load, and it sometimes spiked 98% but didn't crash for 3 whole rounds. Think it might be gone, but knowing my luck, it's probably gonna crash soon again

It will,just when you think it's safe to go back into the water this comes along:
http://scienceblogs.com/lifelines/files/2014/01/13243547332073393725diving-with-great-white-sharks.jpg

You also might want to try playing without any browser open.

I *think* that is what fixed my crash issue. Some flash based video possibly effecting vid memory...

Just going on what you've written here, check your PSU. From the sounds of it it's dying, or faulty.

pretty solid rig you have i see. mine is fx8320 and gtx650 ti. just had one crash after playing 10 days. other than
that im gaming all right. you are not playing BF4 and Witcher3 at the same time are you? coz you are inviting your PC to crash ok. my other guess is that your rig is overheating. so check your temperatures and cooling fans shoud be working. CPU temp should not hit above the 60 degrees celsius to be safe.

No I'm not playing them at the same time xD.
And my CPU tops 50C and my GPU tops 75C. So I don't think its a heating issue.

As Ryuubei said, it might be my PSU, but I want to be 100% sure first before I replace it, because money is an issue of course :P

A wrd of caution, if you suspect the PSU in ANY way, replace it. I learnt the hard way and kept using a PSU i thought was on it's way out, but was also thinking it was just faulty ram. So i replaced the ram and week later the PSU blew and took my CPU with it.

These days if im even a little worried about the PSU i change it, i'd rather be £100 out of pocket on the PSU than having to buy a new CPU or more. Thankfully it's not gotten that bad since i bought a good PSU this time round, but it always worries me :D

If you can stick the PSU in a different system and play a game that you've played on your own, that has consistently caused it to die, suc as W3. If it dies in THAT system as well, you're almost garunteeed its the PSU.

nother alternative is to take the entire system into a store for a full maintenece. Something else i've started to do, since i honestly don't have the time to do. It costs me £40 every 6months or so, but they can spot problems before they get serious. Just make sure it's not a dodgy store that will basically try and milk you for every cent hehe