Gaming Computer Became Slow Overnight

[SpeedH4ck]

My computer was running fine. Then suddenly it can't run games properly anymore. When I mean properly, I used to play mafia 3 max settings, now i try to play max settings, it runs fine for a minute or two but then it starts lagging. When I reduce the quality, same thing happens eventually, maybe after 10 or 20 mins, Right now, I tried on the lowest settings, its lagging on there too. Same thing happened with forza horizon 3 so it cannot be the game. When the computer is in normal use, its fine, CPU usage stays around 10%. I reduced the number of startup programs too but I don't think they affect anything since the normal use of the pc is fine.

Specs:
Operating System: Windows 10 Pro
Processor: AMD A10-7860K Radeon R7
Memory: 16GB RAM
Card: GeForce GTX 1080
Two 1 TB HardDrives (both around half full)

Things I've tried (in order):
- used about 7 or 8 different anti-virus and antimalware programs but found nothing.
- reset win 10, formatted both hard drives
-I used an air duster to clean out any dust.
-I did a ChkDsk on both hard drives.

 

[maz89]

Can you use Windows Restore to restore your system to a point before games became laggy?

Also, try un-installing and doing a fresh install of graphic card drivers.