Fixing HDD and CPU always up to 100%

Today I could fix a case where a computer got incredible slow over the years, but it took to check lots of points...

First of all the issue was initially hard to figure out where it's coming from. 

Either the HDD in the Task Manager went up to 100% or the CPU - or both together. Even when no application was started. Narrowing down which service or application was at fault was difficult as well as it was always another one.

So I tried first with the 'obvious' solution which you find quite often online: Switching off services like 'Windows Search' or 'Superfetch'. Initially it seemed like no change at all. I even checked the hard disk since I even found sites where users where claiming having issues with the Toshiba DT01ACA100. But the HDD was fine so far, nothing visible with checking tools.

So what else... Such issues can come through viruses or malware so I gave Malwarebytes AntiMalware another go. And it found more than 4000 suspicious entries! After clearing them all and going for another reboot, let the software went through after to check if the malware is really gone and suddenly the issues got less!

Surely, right after booting the computer still took a while 'calm down' in terms after processor and hard disk usage. But then you could finally reproduce it by opening the Firefox browser and open certain websites. Or starting MS Office software.

Generally websites using flash took pushed the scale high again, but after certain tests to fix that issue within FF failed and I tried the same with Google Chrome which was faster and and slightly better.

And now after several restarts the computer finally seems fine again - hopefully it remains!