modify autocad drawings
If you can’t modify the graphic after you open the drawing, it is usually because the drawing is encrypted. You can try the following way to fix the problem.
Copy the following code in the notepad, save as unlk.lsp files and then open the drawing can't be modified, command the appload to select and load the unlk.lsp file. Enter unlk in the command line and select the un-modified graphics...
C: (defun unlk (/ en ent)
(setq en (entsel "\ n please select the encrypted graphics:"))
(if (= (CDR (assoc 0 (setq ent (CDR (entget (setq en (car en)))))))
(setq ent (entmakex
(list '(0. "INSERT")
(assoc 2 ent)
(assoc 10 ent)
(the command "_. Explodes" (entlast))
(princ "\ nOK, decryption success.")