el archivo que a mi me sale tiene extensión .sdf
"SDF
Schematic Description Format - the native Labcenter format - used by VSM, ARES and any future Labcenter EDA products. Also very easy to read in and process to other forms. Contains all textual/connectivity information contained in the DSN file.
Use Physical mode for ARES."
es de lo mas normal, se crea y se borra. siempre lo ha tenido el proteus