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correction to previous post - start (bottom left) not safe then power . Sorry

I have same problem and have Bitdefender. I run Windows 10. Windows 10 requires a new free upgrade of Bitdefender - see web site. A workaround - boot computer in safe mode and ccleaner should run. Then reboot normally and it also runs. To boot Windows 10 in safe mode - safe / power - then hold down shift while choosing restart. You will be taken via several screens to safe start.