Never download an .EXE claiming to be the SW decoder from Torrent sites or anonymous file lockers like "upload4ever.com." Always use mirrors from the Internet Archive or known retro communities.
The plugin was originally released as freeware in 1998 by the now-defunct group "Digital Sound Factory." In 2012, the rights were abandoned, placing the software in the public domain / abandonware category for non-commercial use.
Common with MKV or MP4 files utilizing multi-channel AC3 or EAC3 audio tracks.