Function

• The NTUSER.DAT file is a registry file. Each user’s NTUSER.DAT file contains the registry settings for their individual account. The Windows registry, as described by Microsoft, is a "central hierarchical database” that contains information about the software, hardware and user profiles contained on a computer. Windows is constantly referencing its registry files throughout the course of its operation. The configuration of the “HKEY_CURRENT_USER” branch of the registry is supported by the current user’s NTUSER.DAT file.
  
  

Location

• Most of your computer’s registry support files are in the C:\Windows\ System32\Config folder. But the NTUSER.DAT file is unique. It’s in your user folder. In Windows XP, user folders are at C:\Documents and Settings\USER NAME. In Windows 7 and Windows Vista, user folders are at C:\Users\USER NAME.
  
  

Viewing

• The NTUSER.DAT file is a hidden file. Hidden files, as the name implies, cannot be seen unless you configure your folder options to show hidden files. Therefore, if you do not see your NTUSER.DAT file when you initially open your user folder, go to the “Tools” drop-down menu and select “Options.” Click “View,” and in the “Hidden files and folders” section, select “Show hidden files and folders,” and then click “Apply.”
  
  

Warning

• Deleting a NTUSER.DAT file will delete a users preference settings and may corrupt the user’s profile. Because the NTUSER.DAT file is a system file, it’s normally locked in order to protect it from accidental deletion. Only a system administrator, logged into a user account that is different from the account that contains the NTUSER.DAT file you want to delete, and operating in Safe Mode, can delete a NTUSER.DAT file.
  
  

Other

• The NTUSER.DAT log file, which is listed as a text file, backs up the NTUSER.DAT file. If an error occurs in the NTUSER.DAT file, Windows uses the NTUSER.DAT log file to correct it. If a computer is part of a network, it may also have a NTUSER.INI file. NTUSER.INI files are used to create a “roaming profile” for a user that does not get copied to the network server. When the DAT extension of an NTUSER.DAT file is change to NTUSER.MAN it creates a mandatory user profile that is no longer user-configurable. So whenever a user logs off, any changes made to the user’s preference settings are not saved.