When your computer is not working the way you want it to, a basic troubleshooting step is to boot into Safe Mode. When your computer is in Safe Mode, it is not running any of the extra software or drivers you may have installed. It only runs the basic components needed to start your operating system. That way, you can see if one of those programs (or malware) is causing the problems you are experiencing.

Here's how to get into Safe Mode: 

Windows Computers

When your computer is starting up, tap the F8 key on your keyboard continuously until you are presented with the Startup Menu or Windows Advanced Options Menu, depending on your version of Windows. Use the arrow keys on your keyboard to choose Safe Mode from the menu and press Enter.

When you want to get out of Safe Mode, simply shut down and restart your computer. 

Mac OS X Computers

With the computer off, press the Power button. As soon as you hear the startup "dong" noise, press and hold down the Shift key on your keyboard. When you see the gray Apple logo, you can release the Shift key. When MacOS comes up, it will display that you are in Safe Boot mode.