There is only one file type that uses the .ND extension:
QuickBooks Network Data File
Configuration file used by QuickBooks financial accounting software; allows network access to a QuickBooks company file; created when the company file is opened.
NOTE: If the network data file becomes corrupted, you can rename the extension to ".ndold," then open the associated company file. QuickBooks will then create a new network data file.
Updated: September 8, 2009