Unlike .cdx/.mdx files that open automatically when the associated table is opened, you must open a .ndx/.ntx file explicitly using program's Index Manager dialog box (File-> Index manager menu item).
Index files are only relevant for searching in the DBF - you really don't need them (i.e. you CAN read the .dbf data file without the index file). Removing the index file might break you application though.
This is an advanced DBF data management solution for all database users. It is packed with features normally found only in top end software.
Links to dbfmanager.com (6)
astersoft.comManage, Fix, Compare & Sync Your DBF Files | astersoft.com
dbfconv.comDBF Converter - free online conversion service DBF to CSV, Text, HTML and SQL script formats