There is a big difference between a corrupted drawing and one that is encrypted.

If a drawing is corrupted then try using the RECOVER command to open it.  If the drawing can be opened but not saved for some reason then try using the Overkill, -Purge (Regapps then All) and Audit commands on it to clean it up.  Once you do then maybe, just maybe you can save it but I'd recommend saving it under a different name.

If the drawing is encrypted (do you mean password protected?) then kiss it goodbye because you aren't going to open it.  Period.


Edited by John Connor - 17.Nov.2015 at 15:39

If the drawing is encrypted by password protection, it will politely ask for a password on open.

Maybe a quick check suggested by the principal themselves with various steps 

http://knowledge.autodesk.com/support/autocad/troubleshooting/caas/sfdcarticles/sfdcarticles/AutoCAD-File-Corruption.html

Otherwise, try using  DWG Recovery Toolbox s/w just to make the file legitimacy for recovery chances of prev copies.  http://www.oemailrecovery.com/dwg_recovery.html

Hopefully from Autocad autosave by default, it should have saved dwg file automatically with ac$ as default extension, and if we can just find the *.ac$ file and change ac$ to dwg. There may be slight chance. The AutoCAD's autosave file is saved in this folder: C:\Users\[User Name]\appdata\local\temp\. typically.

diego: Attach a copy of the drawing to your next post.  Maybe someone here will have better luck unless of course it is encrypted in which case neither you nor anyone else here will be able to open it without the password.