.SIDN File Extension
File TypeiTunes Authorization Data File
What is a SIDN file?
File used by iTunes, a multimedia playback program; contains information referenced by Windows to play purchased songs for a specific user account; similar to .SIDB and .SIDD files; not meant to be opened manually by the user.
SIDN files are saved to the following directory in Windows 7 and 8:
C:\ProgramData\Apple Computer\iTunes\SC Info\
Windows XP uses this location:
C:\Documents and Settings\All Users\Application Data\Apple Computer\iTunes\SC Info\
NOTE: If you install a new version of iTunes in Windows and it will not open, you can delete the SC Info.sidn file along with the SC Info.sidd and Info.sidb files in your directory as listed above, restart your computer, and then reopen iTunes.