after entering password l/t goes blank and cannot do a thing
entering password and clicking enter m/c goes blank and locks
I asume you mean a toshiba satelite c40 ?
It is a windows 10 laptop?
Is there an erro on the screen? does it reboot after going "blank" ? and in lock you mean error : wrong pasword?
Try to start the laptop in safe mode , try to log on.
or try to reboot the laptop and do a system restore ( due to faults in OS ?)
to start up in safe mode: reboot the laptop and press esc or F12