CPU 100% until I open Task Manager

[gtdadof10]

I have a fairly new computer running Windows 10. My son built it for me as I need CAD from time to time and my old one wasn't powerful enough. At first, all was well. Then it got very slow at times. Sometimes I would sit for 10 or 20 minutes before I could do anything. My son suggested that I open the task manager so I could see what was slowing things down. I noticed that every time I would open the task manager to look, I'd see the cpu % very high, even 100% at times, but it would drop as soon as I started trying to find something. I've purchased and installed Malwarebytes Premium 4.2.1. It found and resolved problems but the main problem persists. 

Any help appreciated.

[exile360]

Greetings,

Please follow the instructions in this topic then create a new topic in our malware removal area by clicking here and a malware removal specialist will guide you in checking and cleaning your system of any threats.

Good luck, and if there is anything else we might assist you with please let us know.

Thanks

[nukecad]

Whilst you should follow the instructions from exile360 to see if the experts can find what is causing the slowdown - don't worry about the Task Manager showing 100%.

That's just the way that the Task Manager in Windows 10 works.

When you open the Task Manager in Win10 it always shows 100% CPU at the top for the first second or so until it calculates what is actually being used.
Open and close (not minimise) Task Manager a few times in a row and you'll see that it always does the same.
(If you quickly look down the column the individual entries will be showing 0%).
Nothing is actually using 100% of the CPU it's just a 'holding' number.
In previous Windows versions Task Manager used to show 0% CPU at the top for the first few seconds, but nobody though that is was actually zero.

Why that changed in Windows 10 you would have to ask Microsoft.