I found a way to stop it from crashing at last (well, it works for me so may help others)

My spec
i5 4670k
GTX 780 ghz ed
16gb RAM
Win 8.1 (64bit)

History: I had this on Steam but its never worked since I built this PC (previous PC was fine). I tried various compatibility modes, verified files, re-installed to either my HDD or SSD,checked all my drivers were up to date and still no joy and I gave up.
But I figured, my system is fine, it runs everything else with no issue so maybe its Steam at fault.
So I bought it on GoG.
Exactly the same issues. I can go through character set up but as soon as the game starts after the first cut scene, I move my character a few steps and CTD.

Tried onboard graphics too by disabling my card. it runs but very slowly (approx 10fps).


Solution: Reduced the speed of my GPU from 1020Mhz to 900Mhz and it runs perfectly. I'm running it in Vista SP2 compatibility

Hopefully someone finds this glaringly obvious solution (yes, I'm kicking myself) useful.