The way AutoCAD defaults, the incremental saves are stored as "autoX.sv$", where X is usually a single digit. The ac$ files I thought held the histories for the command line, undo, etc. I know you can rename the "sv$" to "dwg" and pull your cheeks out of the fire (although it's not always foolproof), but I'm not sure the ac$ files would be readable as a drawing file. What is in there that you need to restore?