I had created tons of details on a single file in AutoCad (2007) and suddenly I saw across the header that the file was "Read Only." Neither I nor anyone else had an additional session of that file open, and I had not intentionally changed any settings to make the file read only. I could not "save as" to save my changes as another file. So I selected all the details I had drawn, right-clicked and selected copy from the right-click menu. Then I created a new file from a template and pasted all the information there. Then that file became read only as well. I didn't know how to change the read only option on the drawing and didn't want to lose the information, and no other CAD users were still at the office, so I left the computer on overnight and in the morning asked another CAD user in the office for help. He said I could try to open the file on his computer. So I closed it on mine and then tried to open it from his computer and got the message "drawing file is invalid." It would not open from his computer, and then when I returned to my computer it wouldn't open from mine either. Is there any way to retrieve the file? It represents hours and hours of work that I can't afford to lose (project deadline this week, and I was fairly close to finishing). Is there any way to get around this and get the file open so I can copy the information again?

did you check your .bak ver of the file?  If you change the .bak to .dwg you can open it, and depending on how often ACAD is set to auto save will depend on how much you mave have lost.

Thanks so much for your reply. How do I convert a bak file to a dwg file? I have tried to open the bak files before but couldn't and didn't know how to convert them. Any help would be appreciated!!

you can change a .bak file to .dwg, making clik with the right side of your mouse, then clik in propierties , next step clik  in name of file ,erase bak and write dwg, thats all.
 
 

Thank you! I tried this but it still won't open with AutoCad - it is still labeled as a BAK file even though the file extension in the name of the file I have changed to DWG. I am using Windows XP and AutoCad 2007...is the procedure in converting files from BAK to DWG different for these versions of the software? Or is there another way to do it?

Ok try using  MSDOS .
1.- Go to find the file command system 32
2.- clik in that file
3.- you are now in msdos,  clik cd..enter
4.-again cd..enter
5.-dir enter
6.-clik cd(name of the carpet where is your bak file)must have 8 characters or less if no change the name.
7.-clik dir
8.-clik ren(name of the file).bak space (name of the file).dwg enter
9.- clik dir     to check the change of name of the file
10.- close with exit 
11.- ok thats all
 
I hope this help you with your problem
 
( sorry by my english, but I only speak spanish )
 
 
7.-

Nope it is the same to matter what file you are trying it on.
 
Try this....
 
1) right click on file
2) select "rename"
3) left click once in the blue area..that should turn it white and you should see blinking cursor.
4) use arrow keys to move cursor the very end....then use backspace key to remove the last 3 letters.....try not to remove "."
5) type "dwg" (without quotes)...then hit "enter".  if you deledted the period you will have to type that in front of the dwg like such ".dwg"