Windows 10: HDD Constantly Running at 100%

Upon startup of my PC its not painfully slow but it isn't as fast as it should be, when I open Task Manager the HDD is running at 100%, and doesn't move from that for maybe half an hour or so, then after that it gets back to normal, so whilst running only the web browser to write this post its now ranging between 2-10%. When it is running at 100% I can't really see whats causing it to run so high. I've tried a few things that I've read like disabling Windows Search but can't tell what the computer is struggling with. Any ideas are much appreciated.
Windows version number - Version 1903

:)

 

HDD running at 100%

My HDD is running at the 100%, when I check the task manager and I am seeing the window services are running duplicates. EX. CONHOST was running at 4x. I attempting to uninstall recent programs to include a MACFEE antivirus in order to resolve the problem
without any success. HELP.

 

CPU constantly at 100%

Being as stubborn as I am for Windows 7, I waited until the last possible second to upgrade to Windows 10. Now that I've upgraded, my CPU is constantly at or near 100% mainly by two processes listed as System and System Interrupts, both running 20-30% each. I looked around and most people say these shouldn't be more than 5-10%.

Before you start suggesting the obvious like checking for updates, flashing BIOS, upgrading drivers, editing Registry, using Process Explorer, going into device manager, checking background apps, using the built in troubleshooters, formatting, erasing previous Win installations, etc. Let me just say, that I've tried all of those and none of them seemed to work. I can get the CPU down to about 50-60% but that still seems like quite a lot for a freshly booted up PC just sitting on standby.

At this point, I'm looking for any suggestions at all. My best guess is that maybe my laptops just too old? I've had it for close to 5-6 years or so and I never replaced any of the parts, so it may just be that it's just getting harder to run modern OS? I don't know. If there's any other options, I'd love to hear them before I start looking into replacements.

 

100% Usage on Secondary HDD

I'm sure that isn't a problem with my HDD. I've just bought this brand new WD 4TB HDD. And on the top of this inquiry, I mentioned that something wired is that the 100% usage jumps between HDDs. It's disk E,F,G this time and it would be disk C,D or H,L next
time after I restart.(I have 3 Secondary Hdds).

The 100% occurs only when some applications are making use of the disk, such as file copying.