There are several methods how to try to open a corrupted AutoCAD drawing file.

·        Use the Recover command

·        Open the file and press ESC key just before Regeneration/Error message, save to DXF, load, save as DWG, Audit

·        Insert the complaining DWG as a block into an empty drawing

·        Open/save the DWG in an older version of AutoCAD or AutoCAD LT or Actrix
Or use 

Photoshop Restore Toolbox from http://www.photoshop.restoretools.com/