NTUSER.MAN is a special type of registry file used in Microsoft Windows operating systems. Unlike the standard NTUSER.DAT file, which stores user-specific registry settings and is modifiable, NTUSER.MAN is a mandatory profile file. When a user logs in, Windows loads NTUSER.MAN and applies its registry settings, but any changes the user makes during the session are not saved back to the file. This ensures that user settings revert to the administrator-defined defaults at each login. NTUSER.MAN is commonly used in environments like schools or businesses, where it is important to enforce consistent user configurations and prevent unauthorized changes to system settings. The file is typically located in the user's profile directory on the server or local machine.