I have finally got all the answers, which is rather nice, and this topic shows my evolution with my computer, and how i changed many things, until the last one was the broken part.
Anyway, the HDD was broken. In the end i took everything off it by externally connecting it to my laptop, then i wiped it.
And the thing stopping my computer from posting? The CPU. I put the processor in an old motherboard, and it would not post. I put the old processor in the old motherboard, and it worked fine. So, now i need to shop for a new processor!