There is only one file type that uses the .NEU extension:
Pro/ENGINEER Neutral File
File created by Pro/ENGINEER, a program used for 3D product design; contains part information, including geometry, layering, appearance, parameter data, materials, and other design information; stores parts in a neutral format so they can be imported into other CAD programs.
NEU files can be converted into other common CAD program formats, including .STEP, .IGES, .DXF, and .DWG.
Updated: August 25, 2010