Heavy Lag when CPU is under even moderate load

[Tieox]

As per the title really, I can be running various tasks and typing in another window becomes VERY laggy.  I was decompressing an archive with process manager showing 30% usage on my 6700k (stock clocks/voltage) and the whole system seriously slowed down to where typing would show a single character per second. 

 

This happens also when you tab out of games during a load screen, again the CPU/GPU/RAM is nowhere near maximum load yet WIndows slows down as if you have seven Cinebench runs going on!. 

 

Specs:

 

Intel 6700K (stock clocks/voltages)

16GB DDR 2133mhz 2x8GB (stock bar XMP)

250GB 860 OS, 250GB 850 Games and 500GB 840 Games.

Gigabyte G1 GTX 1080

Latest Windows 10 version, recently re-installed to try and fix this.

Latest Nvidia drivers clean installed.

 

AV is Defender, and Malwarebytes free. 

 

 

This has only started to become an issue the past few weeks, nothing in my configuration has changed, nor my usage hence my noticing a serious drop in performance even when under minor load.

 

 

[Sjaakie]

How are the temps? Maybe a drive issue, check health with something like crystaldiskinfo.

[Tieox]

Temps are solid, and given they're all Samsung SSD's they're fine the 250GB's are high in the total writs but are passing all health checks.