AutoCad 2009. Program failure

I had a trouble. I worked in AutoCad 2009. When dragging part of the drawing there was a program failure. I found the file with expansion of .sv$ but I can't rename it into .dwg.
the drawing was, for example 111.sv$, and to become 111.dwg.sv$
What to do? Please, help!

I was helped by the following:
1) tools - folder options - view - uncheck "hide the registered file types". Still I recommend.
2) to use TotalComander or DWG Recovery Kit.
But I was helped by DWG Recovery Kit
http://www.all-recovery-inc.com/#!/dwg
On the forum you can see more tips.
http://www.filerepairforum.com/forum...Damaged files?
Good luck and more often save your work!!!

have the same issue helP!