Computer Freezes Up

[RednaxL]

Hello.

Last Saturday (November 28th, 2020) I received an HP Compaq 6200 Pro MT computer, previously owned by a small agency that helps people with a low financial income - but that is irrelevant. The computer came with a WD Blue HDD running Ubuntu (locked out, because they never reset it). I swapped the HDD out for a smaller, laptop-sized HDD that I had lying around and installed Windows 7 on it. I quickly remembered that Windows 7 has been made obsolete because support has been dropped not too long ago. So I installed Windows 10 Home 64-bit on it. It seemed to work fine, but it was slow, and already showed me the freezing issue once. I disregarded it as a fact of "the drive is old" so I swapped it out for a Samsung EVO 860 250GB SSD.

Unfortunately, the freezing issue persisted. I have no idea what is causing it, but it is starting to get on my nerves. This is a list of things I have done; both advised and Google searched:
- I ran memtest.exe to test the memory.
- I ran the IPDT tool from Intel for the CPU.
- I san a CMD command "sfc /scannow", which only found corrupted files once and never again.
- I messed around the BIOS/UEFI to try and diagnose the issue.
- I booted up the Windows Memory Diagnostic program over 5 times.
- I dusted out the tower, reseated the RAM, and reseated the CPU (and refreshed the thermal paste).
- I reinstalled Windows 10 once.
- I changed SATA ports.

- I even ran the HP PC Hardware Diagnostic Tool.

I am at a loss, because my knowledge about this only goes so far. The computer doesn't even have to be under a workload. The last time it crashed, I had booted it up, briefly focussed on another PC, and then turned back to it, only to move the mouse and figure out it had frozen yet again. No bluescreen, just freezing.

These are the specs (not 100% verbatim):
MOTHERBOARD - Intel Q65 Express.
CPU - Intel Core i3-2100 at 3.10Ghz.
GPU - Intel Integrated HD graphics.
PSU - UNK.

RAM - Stock DDR3 2x2GB (making 4GB total) at... 1330hz?

SSD - Samsung EVO 860 250GB running Windows 10 Home 64-bit.

I need assistance, because I am out of moves.