If you cannot log into the laptop using a system password, not referring to the Windows password, Then you will have to call Dell tech support. After confirming that you are the registered owner they can assist you accessing the laptop. There may be a charge for this service as well.
I have updated my laptop by resetting factory settings and now system is not allowing me to sign in. Password window is not working. Plz help 
After reset system is not let me sign in