New pc slow.

[Twixxin]

So my cousin bought a brand new pc with those specs:
Intel Pentium G4560
Asus H110M-R
Samsung 8 GB 2133 MHz
Toshiba 1tb 7200rpm sata 3
Inno3D GTX1050-Ti 4 GB
LC Power 600H-12
MS Phantom
Prebuilt pc, it booted very slow first time having bunch of bloatwares we didn't need so I reinstalled the windows. It still feels very slow, i tried bunch of tweaks but nothing. How should and I approach the situation since i am not really sure what to do. I've checked with defraggler(also 13% of defrag takes like 24 hours to defrag which is like wayy to long, 13% on my 5200rpm takes like 20min), says disk state is good and brand new with 2 hours of use. Of course I updated the windows before doing anything and installed latest LAN,audio,chipest drivers still no help. I've tried few games they run ok but few micro stutters here and there which are 100% hdd related. Tried changing page file to size of the ram which is 8gb and putting max size to 16gb, but he said it's still slow maybe a bit faster. Pc is at his house atm. Any ideas how should I approach the situation and what to do so i can hopefully fix the problem, since i feel hdd is fine it's just something like bottlenecking it.
Thanks

Edited December 22, 2017 by Twixxin

[Porthos]

32 minutes ago, Twixxin said:

Intel Pentium G4560

Biggest Issue right here.