Pc Mouse , keyboard and case buttons unresponsive and the screen goes black.

[Varticus]

Rig -
Amd 8350 4.0 ghz octa core cpu
Pny quadro 630 gpu
8gb crucial ddr3 ram (2×4gb)
Gigabyte a970 mobo
1tb seagate hdd

The problem began about a year ago where the monitor would go black ans say no input , the keyboard and the mouse wouldnt be responsive no lights ect but the fans, leds and pc would still be powered. I tried to see if it was hardware so i replaced the monitor and it still didnt work, the ram is brand new and that hasnt changed anything , the hard drive i have changed twice (tried a ssd and another hdd) ive tried reinstalling windows 10, windows 7 and so on and have had no change. It usually gets to the boot screen then dies but sometimes it will get past the boot screen and let me log in , loads up a programme or two and then dies. It dies in safe mode but it will run with the hdd unplugged and just sit in bios wich is saying its a software problem?
Ive bought 3 new harddrives for this pc and i dont want to be shelling out for another if its not the case. Has anyone got any ideas on what it coukd be, motherboard or power supply (mines a 850w generic one from a computer shop btw ) also ive swapped out my gpu for 2 others and it does the same thing every time.

Thanks in advance for any help you can give.

 

[Kasper Jorgensen]

With everything you already done, i would say it's either a faulty mobo or CPU. Maybe you CPU is getting too hot, try remove the cooler and re apply thermal paste and also make sure the cpu cooler is spinning.
Also did you install Windows from scratch after changing harddrives.