Pc running very slow

[MJ.Geramian]

hello everyone, recently I bought an industrial laptop (dell precision m6600)
it was ok fast and smooth even I had run a quick play of (CDD).

The next day I eject HDD and installed it again and after a while my pc running slow, I install windows again and system running up it was pretty fast and smooth but after a few minutes, it was fully laggy and slow before installing the GPU driver.

this is my proceedings to find the problem but doesn't work any:
I run a hardware test with pass mark and it almost doesn't find any errors.
I ejected the HDD and installed windows on SSD.
ejected the SSD and installed windows on HDD.
replaced ram(s).
Ejected battery and run with power.
Run only with battery.

pc steel Fluctuates between fast and slow after a while.

what is the problem, masters?

[Whiro]

Whats the specs of this laptop?

[MJ.Geramian]

1 hour ago, Whiro said:

Whats the specs of this laptop?

i7 2620m --- Quadro 3000m --- SSD --- HDD --- ram 16g