This is the display format associated with the broadcast of slow-scan television. This legacy format was used to transmit a static image given limited bandwidth through the use of specialized software.
The SXW file format was originally created for StarOffice Writer, the word processing application for Sun Microsystem's StarOffice suite. Programs that can open SXW files include StarOffice Writer and OpenOffice.org Writer. To open an SXW file in Microsoft Word, it's usually possible by renaming it as a DOC file.