Boot into Safe Mode with Networking by tapping F8 repeatedly while booting up and follow the instructions for the use of Malwarebytes Free (see the last link in my signature below) in that mode (it will download, update and run in that mode assuming your computer allows an Internet connection in that mode.
If it doesn't allow one then at least try using System Restore to go back to before this all started.
Also note that you can right-click the taskbar icon in Safe Mode and select 'Scan' and VirusScan will run silently.
This could also be an indication that you computer is overheating so check that vents are clean, fans are working etc. etc.