Temperamental Mobo/HDD?

[Stone21]

Okay so since the 25th when the problems disappeared. They've returned with a vengeance and it's more serious this time. Today i turned it on, and the BIOS screen refused to appear along with the CPU fan screaming itself to death. So. I thought it's unlikely to be the HDD, but i took it out of my PC and plugged it into another PC i knew was functioning correctly to rule it out entirely, and surprise surprise, the HDD was actually fine. On Windows 10 with my HDD on it the old lower spec PC i have kicking around booted in under 6 seconds.

By the time i came back, plugged my HDD back in and hit the power button on my PC, it started up as normal, until it got to the Windows Logo, now this thing was spinning away to itself for a while. Like. 35 minutes almost before it finally came up. Whenever i click something, for example, it takes a good 5 seconds for it to respond. In fact at one point it froze altogether, black screened then went off. Hit the power button again, fan went ballistic and then it booted as normal. Right into the same sluggish shenanigans. I'm actually stumped. Since the other PC going about is an AMD machine, so it's not like i can swap Intel CPUs around (supposing they were the same socket) to rule that out also. Anyone know any in depth hardware diagnostic software or has what I've described indicate imminent motherboard failure? Cheers for the input. Starting to get sick of using my laptop and it's crappy Pentium

Did you try to test the said HDDs with new SATA cables? Maybe the ones used in your Intel PC are causing trouble? Maybe the PSU cables are also causing problems or maybe the motherboard is about to fail. There are many paths to follow.. I would take the PC with me to a service to check it.