The s7s file extension is used for firmware files for Sony Ericsson S700i mobile phones.
Most likely some old format without support from developer. No further information could be found.
How to open:
Probably the only way to access this file is to upload it to the phone through upgrade function.
How to convert:
As far as we know, this .s7s file type can't be converted to any other file format. This is usually the case of system, configuration, temporary, or data files containing data exclusive to only one software and used for its own purposes. Also some proprietary or closed file formats cannot be converted to more common file types in order to protect the intellectual property of the developer, which is for example the case of some DRM-protected multimedia files.