Answer:
Press the function key F8 to boot into safe mode and log in as User15. Then, remove extraneous startup programs.
Step-by-step explanation:
This is a problem that is related to a missing or corrupt system file responsible for managing user accounts and profiles on a computer system.
In this scenario, a user attempts to log in to a Windows PC, but the computer returns to the login screen after entering the correct username and password. A technician inspects the logs in Event Viewer and finds a message that corresponds to the user's login attempts: The user profile for User l5 could not be loaded. Ntuser.dat is missing or corrupt.
Thus, what would be most appropriate for resolving this issue is to press the function key, F8 to boot into safe mode and log in as User15 and then remove extraneous startup programs that are running in the background while a computer is booting (startup).