My drwg crashed, and I went into the autosave and tried to rename the last saved drwg into a .dwg. but it does not turn the saved drwg into an autocad drwg. Do you know if there is something new I have to do? what good is the save if I can't use the drwg?
You should try the Drawing Recover Manager instead. You can access it under the Big A in drawing utilities or just type DRAWINGRECOVERY instead. When you crash out of autocad it should save an autosave copy here if the autosave is newer than the last saved drawing. It will allow you to open either one. Additionally you should go into your options and either set the autosave to a value you can live with or just make sure that you hit the save button as often as you feel comfortable.
P.S. In the future you should name the subject of your posts a little better. It will help people who are trying to help find the posts to which they know the answers to and in addition it will help others in the future to effeciently find a post that might hold an answer to their problem.