.idx - Outlook Express Mailbox Index (Microsoft). ( file extension )

.iff - Image File Format. Used by Sun computers for image files.

.iff - Interchange File Format. Used to transfer documents containing various data types, such as graphcs and sound, between Amiga computers.

.imf - MIDI Music File ( file extension ).

.img - Image file format. Originally designed for use with the GEM paint program. It handles monochrome and gray scale images. ( file extension )

.imj - Image JPEG format. Variation of the .jfif file format with a Microsoft Windows .bmp header and enhanced palette optimization.

.imp - DVD file.

.ini - Initialization file. Utilized by Windows OSs to initialize certain system operations. ( file extension )

.inf - Information format. An ASCII text file. Also used by Microsoft as a type of installation file.

.inst - 3D graphic file.

.int - Intermediate Code Used for Syntax Checking.

.inv - Windows Update file.

.ipd - BlackBerry Backup File (Research In Motion Limited).

.ipg - iPod Game Package (Apple Inc.).

.ish - Compressed file archive created by ISH. ( file extension )

.iso - Easy CD Creator Disc Image. ( file extension )

.ix - WordPerfect Office Template File -Corel Corporation. ( file extension )