Have you started up in safe mode?
Have you started up in safe mode? When you turn your computer on press F8 to pull up your startup options, arrow down to safemode with command prompt.
Does it work that way?
Your problem sounds like it could be a virus.
I would suggest that you download a program like Malwarebytes, its free and you can download right from their site. If there is a virus this program will most likely catch it
Try both of these and post back