Comprehensive source: http://www.filerepairforum.com/foru...-cannot-open-file-open-cad-drawing-dwg-format – must be helpful to you, forum contains some interesting thoughts about .dwg files
If the drawing file (DWG) still not opens, perform the following steps in the order listed:
Open the drawing file
Type PURGE at the command line. With all checkboxes checked on, click Purge All.
Purge Registered Applications (from the command line):
-Purge
"R" for Regapps (registered applications), then Enter
"N" when asked to verify each name to be purged, then Enter
Purge All (from the command line):
-Purge
"A" for All, then Enter
"N" when asked to verify each name to be purged, then Enter
Audit and fix any errors
Type AUDIT at the command line
"Y" for Yes to fix any errors, then Enter
Save the drawing file
If previous solutions aren’t helpful to you, try to use
DWG Viewer Tool
Demo version:-
http://www.dwg.viewertool.com/
