What can be done to find out which program or process is slowing down the computer. And how to terminate it…?
For windows 10 press Ctrl-Alt-Del to start task manager, select the processes tab and find out which process is using up the most resources. Some of these can be terminated there or by disabling them from the startup tab
Additionally if your disk usage is high in performance tab, you might benefit from a larger hard drive or changing to an SSD which performs better