There is only one file type that uses the .XDI extension:
WinArchiver Extended Disc Image File
Compressed disc image created by WinArchiver, a file compression, spanning, and encryption program for Windows; saved in a proprietary format but can be decompressed to the standard .ISO format using WinArchiver'smenu option.
XDI files can also be mounted as virtual drives using WinArchiver Virtual Drive.
Updated: December 11, 2011