Micha,
Neither the -overwrite_original_in_place or -overwrite_original
options will preserve a "_original" file. If the _original files
were created with a previous command, then you should delete
them if you don't want them. In a Unix shell, this is done with
"rm *_original" (although not recursively). In Windows, something
like "del *.*_original" may work.
- Phil