Question Extremely slow computer that seems literally impossible to fix

[urutule15]

I'm really having a problem here. So, I just got this computer (not new, old), and it had reinstalled Windows 10 on it, 4 gb of ddr3 ram + an intel i3 540. Windows 10 took way too long to boot and I have seen it boot better on Core 2 Duos. I tried doing normal things but it really didn't work. I assumed it was a bad install, so I tried Lubuntu. Lubuntu kinda started faster but still slow. I decided to try and install it, and when I rebooted the computer, it did not boot. I tried to go back to the USB and it locked me out. Could not boot at all, I got three errors, first one being something about srst failed. I looked it up and it was something about the cache on my USB hard drive and that it still booted anyway. I waited 10 minutes, maybe 15 and the only thing that happened was a font change to the errors. I tried to get a Windows 7 install, and every single click took about 2 minutes for it to register, accompanied by the loading cursor. Then when I tried to hit the install button, I waited 15 minutes and it still didn't work. The guy that had this PC is pretty knowledgeable about tech like this and said it was memory. My friend heard about my situation and decided to give me his DDR3 memory 4GB that was laying around. I tried it. Still did not work. I tried getting Hiren's Boot CD on the PC. Still doesn't work. I ran Mini Windows XP and it never loaded. I tried Parted Magic which did not work at all either. Then I tried what could have been the answer to all my problems, MemTest 86. It showed that the clock for my memory was 665 MHz when it was supposed to be 1333 MHz. I'm running around in circles, thinking it might either be faulty motherboard, faulty ram, faulty ram slot, or maybe something's underpowered, I really don't know. If someone can help me that would be great. Thanks.

 

[rgd1101]

cpu temp?
run any hdd health check?

 

[urutule15]

cpu temp?
run any hdd health check?

Definitely is not the hdd. CPU's fine.