Trouble opening a file after system hang

[Siberian]

My system had some lagging/hang issues just now while working on a drawing, and as a result I now get the message Drawing file is not valid when trying to open it. What to do?!?

[Dipali]

open auotcad first, than use recover under file drop down menu to open your file. It may work.
Also you can rename the last .bak file as .dwg & open it than save it as your drawing.