Why is my computer always working at full capacity even when idle?
You have to see what program is running when you start the pc.
One of the cases that happened to me a lot was in windows 8.1 that was put to automatically analyze if there are updates and put the pc to the maximum, you have to go into update and disable it or see if it is scheduled if you do not want to disable it in case you want to update a program that asks as it happened to me and gave me error and I did not remember that I had disabled it and could not use the program, because I updated it to win10 and I had that problem.
It may be a faulty resident application. I remember reinstalling the operating system once because of the same problem, and when reinstalling the usual applications I was monitoring between each one. There was one that replaced system libraries with an obsolete version that generated a conflict, searching on the internet only in a forum someone had already discovered the problem, but the support was lousy. Reinstall again and never use that application again, problem solved.
No doubt there is more than one possible cause, you must diagnose your case.
You should specify what you mean by working at maximum. If you are referring to fan noise it may be due to thermal tuning problems. On the other hand, if you refer to freezes or see a high resource consumption in the task manager, it may be that one of your components is having problems, the most likely being the hard drive.
that is synonymous of virus or trojans ,
I usually press ctrl+alt+delete( del )
and there is in task manager , close processes that are using resources , as long as there is no program running , to use the task manager better ask in google .
it is also usually effective the netscan , which gives you the open ports to internet and those that are active to pass then some antitrojan .