.NDX - Index - dBASE
.NET - Network file ( filename extension net ).
.NFO - File type nfo can designate a Novell netware folio help file format. An .nfo extension is sometimes used to denote an information file and can be opened with a text editor. ( file extension .nfo )
.NG - Norton Guide documentation
.NLM - NLM program - NetWare
.NOTEBOOK - Notebook created with SMART Board Tools. It may contain text, images, audio and video files, Flash animations, and other objects. It is often used with SMART Notebook whiteboarding software for educational purposes.
.NS4 - A database file created by Lotus Notes 4.x, It may contain a list of contacts, e-mail messages, text notes, a calendar, and other information. The Notes program may also be used for instant messaging.
.NRG - File type nrg can designate a Norton registration entry. NRG file can also signafy a Nero software CD/DVD image file format. ( file extension .nrg )
.NT - System file such as CONFIG.NT or AUTOEXEC.NT that is loaded during the Windows NT boot process. It contains settings and scripts that load resources for the Windows operating system. It must not be modified, moved, or deleted or the computer may not be able to start up.
.NTF - Notes Template File - Lotus Notes database ( filename extension ntf ).