There is only one file type that uses the .ND5 extension:
Renamed NDS File
Nintendo DS game ROM in which the file extension has been renamed from ".nds" to ".nd5"; contains a copy of a Nintendo DS game that be played on a PC using a Nintendo DS emulator.
NOTE: In order to open an ND5 file, the extension may first need to be changed back to .NDS.
Updated: January 31, 2011