|Your system may have an infection that slipped past your antivirus program.|
-> Run Malwarebytes to find and remove the problem.
You could have unnecessary programs running in the background/
-> Uninstall programs you do not need. Run msconfig, go to Start Tab and uncheck all except Microsoft and your antivirus program.
Your antivirus program may be hogging resources.
-> If you have Norton or McAfee, uninstall and install Free version of Avast. To completely uninstall these two programs you need to download their uninstaller from their respective website.
You are inadvertently participating in a participating in a program by a University or organization that uses your computer and many others to process enormous data as a single supercomputer.
-> Uninstall their program and Google any program on your system you do not understand its purpose or who installed it.
--->Install Process Explorer from Microsoft to better understand what is running on your system and decide what to leave, what to remove, and what to use manually only when you want it.
You have to be a little bit crazy to keep you from going insane.