My computer crashed "recently" and is now unbearably slow

[bobellz]

So after crashing, my computer has been unable to install the drivers of my gpu without crashing (tried multiple gpus) and is so slow that it is basically unusable, i did the intel cpu test and it said it was fine, bought a new motherboard and that didn't fix the problem and have tried different ram, also did not fix the problem, also tried a different psu, also didnt fix the problem
I am now stuck, with no idea what could possibly be the issue, ive tried multiple fresh windows installs with 3 different hard drives, all giving the same end result, the computer is usable without a gpu in just very very slow, but i just get a blank screen with a gpu in.
Any help would be greatly appreciated

 

[rgd1101]

What is the full system spec? include make and model of the psu

 

[bobellz]

Gigabyte z270 hd3 mobo, previously msi z270 sli mobo, 2x hyperx ddr4 4gig ram sticks, cooler master b600 ver.2 psu, i5 7600k 1151 cpu, gpus were gtx 760 and gtx 970 neither currently installed