Unknown issue - Either faulty HDD, Memory or interference with my PS4.

No I haven't checked disk yet because it takes time. I'll do when I sleep. And I don't think i've got any electrical issues. Just wanna say that the lag spikes are pretty much gone for now. Good sign.

Ok I had a look in event viewer just now. This was right when I booted up after coming back from work, pc shut down for hours. This is when it took forever to log on and didn't work. It's mostly timeout errors, one is about cdrom, rest about multiple programs like Kaspersky, Skype updater, Malwarebytes and such.

SOLVED:

Everything got worse after my last reply on here. I changed hardrive, lucky me I had a spare one, that is also better than what I had :P. Turns out, I still had my pc lagging hardcore even after a fresh install. So I figured it was not a w7 problem. I went into bios, resetted the settings to optimized, but then my w7 would crash and I was stuck in a boot loop. Anyway, I reinstalled windows but ended up getting hardware error. I went back into bios, changed sata mode to AHCI and it worked. Lag was still semi present, so it was neither my hardrive, windows 7 or bios. Leaves me only one more option, my RAM.

Although ram test showed nothing, neither the graphs, I removed one of my ram sticks and strangely, all of the lag, freezing, ''not responding'' is entirely gone. I guess the stick was partially damaged. Like I said, i did push it to 97% usage at one point.

Anyways, solved!