DRagor :
So I assume the machine has been working fine for 2 years?
In that case, most likely causes are GPU and PSU. Motherboard unlikely.
Without full specs can't get better guess.
well i started off with a gtx 660 which got replaced with a gtx 760 a year later. now 3 years in it was working fine but about in the recent year I had cpu related bsods maybe once a week. now since the last month ive been getting hard freezes pretty much once a day, its like the cpu doesnt get enough power then hangs is my guess.
ive tested without gpu and no freezes for about a week then I became bored and put it back in so I could play games.
The problem is very intermittent so its hard to diagnose, it only happens like once every 20 hours of uptime. I dont want to buy a graphics card and find out it was the psu and vice versa.
specs: i5 3570k, gtx760, 8gb ddr3 ram, windows10, p8z77-lx motherboard, nothing is overclocked and ive reset cmos and hard reinstall w10.