There is only one file type that uses the .UNT extension:
AutoCAD Unit Definition File
Settings file used by AutoCAD, a CAD productivity application used for drafting 2D and 3D designs; contains unit definitions and scales, such as conversions between miles and kilometers or Fahrenheit and Celsius; ensures that the proper units, scales, and unit conversions are used within a drawing.
UNT files are automatically referenced by AutoCAD for converting units. They are stored in an application installation file named acad.unt. UNT files are saved in a text format and can be viewed with any text editor.
Updated: March 1, 2011