I

File extensions starting with the letter I...

  .I    Progress Include File
  .IAF  MS Outlook 97 and 2000 E-mail Account Settings
  .IAN  Sterling Software COOL Business Team Model File  Sterling merged with Computer Associates.
  .IBA  MDE InfoHandler Infobase File
  .IBM  Image File
  .ICA  Citrix File
        IOCA Graphics File
  .ICB  Targa Bitmap
  .ICC  Kodak Printer Image
  .ICE  Archive File
  .ICL  Icon Library File (various) ImageForge/IconForge  [Viewer]
  .ICM  Image Color Matching Profile File
  .ICN  Icon Program
  .ICO  Icon  [Viewer]
  .ICS  Outlook Calendar File
        SwiftView Command File
  .ID   Disk Identification File
        Lotus Notes ID File
  .IDA  MS Server File (default.ida is attacked by the Code Red Worm)
  .IDB  MS Developer Intermediate File
  .IDD  MIDI Instrument Definition
  .IDE  Integrated Development Environment Configuration File
  .IDF  MIDI Instruments Drivers File
  .IDQ  Internet Data Query File
  .IDW  Aldus IntelliDraw Vector Graphic
  .IDX  Index (multiple programs)
  .IEF  Image File
  .IES  Photometric File Data [Illuminating Engineering Society]
  .IFD  Jet Form Design Form
  .IFF  Graphic, Sound (Interchangeable File Format)  [Viewer]
  .IFS  OS/2 System File
        IconForge Image EXE Library
  .IGF  Inset Systems Metafile
  .IGS  IGES-Format
  .IIF  QuickBooks for Windows Interchange File
  .III  Intel Phone Compatible
  .IL   Icon Library
  .IM8  Sun Raster Graphic
  .IMA  WinImage File
  .IMF  ImageForge/ImageForge Image EXE Library
  .IMG  Bitmap Graphic (several programs)  [Viewer]
        CloneCd Related File
  .IMP  Urban Chaos Game File
        Lotus Improv Spreadsheet
  .IN3  Harvard Input Device Driver (Harvard Graphics taken over by Serif)
  .INC  Include File (various)
  .IND  dBase IV or DataPerfect Index
  .INF  Information or Setup File
  .INI  Initialization file (many)
  .INK  Pantone Reference File
        Mimio Ink File [Electronic Whiteboard]
  .INL  MS Visual C++ Inline Function File
  .INP  Oracle Source Code
  .INS  Internet Communication Setting
        WordPerfect File
        Ensoniq EPS Family Instrument
        Sample Cell / II Instrument
        InstallShield Script
        X-Internet Sign-up File
        Inspiration Mind Mapping Software File
  .INT  Borland Interface Units
        Foxpro Code Page
        Intermediate Code used for syntax checking (various)
  .INX  Foxbase Index
  .IO   Compressed Archive  
  .IOB  Imagine File
  .IOF  Findit Document
  .ION  Text Program/Installation Description
  .IPD  InstallPROG 6 EDBS Install Database
  .IPF  Microsoft SMS Installer Script (with System Management Server 2.0)
  .IPL  Corel Pantone Spot Reference Palette
        InstallPROG 6 EDBS File Library
  .IPX  Interactive Pictures Corporation AV File
  .IQY  Excel Web Query
  .IRS  WordPerfect Resource File
  .ISD  RapidFile Dictionary
  .ISH  Compressed Archive File
  .ISO  File List for CD-ROM
        ISO Buster File
  .ISP  X-Internet Sign-up File
        Internet Communication Settings
  .ISS  InstallShield Response File
  .IST  Digitrakker Instrument File (by n-FaCToR)
  .ISU  InstallShield Uninstall Script
        Netscape File
  .IT   Impulse Tracker Music Module
  .ITI  Impulse Tracker Instrument
  .ITS  Internet Document Set
        Impulse Tracker Sample
  .IV   VRML File
        Open Inventor File
  .IVF  Indeo Video File
  .IW   Iconware Application
        Idlewild Screensaver
  .IWA  IBM Writing Assistant Text
  .IWC  Installwatch Database (install monitor)
  .IWP  Wang Text File
  .IX   Framemaker Index File
        Paperport Search File