.??_  Files ending in "_" are often compressed install files of the same
          name (e.g., .EX_ expands to .EXE, .DL_ expands to .DLL, etc.)
  .I    Progress Include File
        Borland C++ Intermediate File
        INTERCAL File (INTERCAL=Compiler Language With No Pronounceable Acronym)
  .I17  Pixel Power Collage  [XnView]
  .I18  Pixel Power Collage  [XnView]
  .I2S  Invision for mIRC Settings
  .I66  Interactive66 Graphic Design Information
  .IAF  MS Outlook 97 and 2000 E-mail Account Settings
  .IAM  Autodesk Inventor CAD File
  .IAN  Sterling Software COOL Business Team Model File  Sterling merged with Computer Associates.
  .IAP  TeamBG File (modify Infinity Engine games)
  .IAX  IBM Image Access Executive Bitmap
  .IB7  Pixel Power Collage  [XnView]
  .IBA  MDE InfoHandler Infobase File
  .IBF  Instant Backup
  .IBM  Electronic Arts Deluxe Paint  [XnView]
        Archdos Compressed File (IBM internal file)
  .IBS  i2 iBase File
  .IBX  Interscope BlackBox File (encryption program)
  .ICA  Citrix File
        Image Object Content Architecture (IOCA) Graphics File  [XnView]
  .ICB  Targa Bitmap
        Image Capture Board  [XnView]
  .ICC  Kodak Printer Image
        IronCAD Catalog
  .ICD  IronCAD 2D CAD File
        ASTi Model Builder File
        Rate Structure File (BLDRATE.EXE input)
        File Associated with Many Games
  .ICE  Archive File
  .ICF  ICOM CS-2100 Radio Programming Data
        Insane Chat Saved Conversation [ASCII file] (Use care entering this site)
  .ICL  Icon Library File (various) ImageForge/IconForge  Microangelo  [XnView] [IrfanView]
  .ICM  Image Color Matching Profile File
        ICC Profile, Acer Monotor Drive
  .ICN  Icon Program
        AT&T Graphic Format
        RIPTerm Image  [XnView]
  .ICO  Icon ImageForge/IconForge  Microangelo  [IrfanView]
        GIMP Icon  [GIMP]  [XnView]
        Sun Icon/Cursor  [XnView]
  .ICON  Sun Icon/Cursor  [XnView]
  .ICQ  ICQ Saved File
  .ICS  Outlook Calendar File [Buy Office XP at Shop.Microsoft]
        SwiftView Command File
        IronCAD 3D CAD File
        Inovate 3D CAD File
  .ICW  InterCAD File (Polish site)
  .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
        Database Used by Disassembler
  .IDC  Core IDC  [XnView]
  .IDD  MIDI Instrument Definition
  .IDE  Integrated Development Environment Configuration File
        Sophos Anti-Virus Virus IDEntity File
        Borland C++ Project
  .IDF  MIDI Instruments Drivers File
  .IDI  i-deas Web ACCESS File
  .IDIF  Netscape Saved Address Book
  .IDL  MS Visual C++ Interface Definition File
        OMG CORBA Interface Definition Language
  .IDQ  Internet Data Query File
  .IDT  Output of DLL2IDT Utility (used in disassembly)
        Text Archive Table (used in software development)
  .IDV  Autodesk Inventor Design View Tree
  .IDW  Aldus IntelliDraw Vector Graphic
        Autodesk Inventor CAD File
  .IDX  Index (multiple programs)
  .IDY  Debug Information File (IMS Database related)
  .IDZ  i-deas Web ACCESS File
  .IEF  Image File
  .IES  Photometric File Data [Illuminating Engineering Society]
  .IF9  Pixel Power Collage  [XnView]
  .IFD  Jet Form Design Form
  .IFF  Graphic, Sound (Interchangeable File Format)  [XnView] [IrfanView]
        The Sims (Maxis) Object/Data File
        Sun TAAC Image File  [XnView]
  .IFM  Brighterion iPrevent Fraud Model
  .IFO  DVD Info File (contains menus and other information)
  .IFP  KnowledgeMan Script
  .IFS  OS/2 Warp Installable File System
        IconForge Image EXE Library
        Yuvpak Compressed Fractal Image
  .IFW  Luminosity Impact! File
  .IFX  ImageSoft v2.00 Graphic
  .IGES  IGES-Format [IGES Info]
  .IGF  Inset Systems Metafile
  .IGNORE  Likely a text file (e.g., README.IGNORE)
  .IGP  Igor Reader Sheet Music File
  .IGR  Intergraph SmartSketch Drawing
  .IGS  IGES-Format [IGES Info]
  .IGX  iGrafx Process (graphical process modeling and simulation)
  .II   C64 Doodle Compressed File  [XnView]
  .IIF  QuickBooks for Windows Interchange File
  .III  Intel Phone Compatible
  .IIM  Interscope InstallMaster Setup Project
        Inshape Graphic  [XnView]
        iOpus Internet Macro
  .IIMG  Interleaf Graphic  [XnView]
  .IJS  Text File
        File Often Associated with J.EXE (not certain what J.EXE does)
  .IKL  MS InkBall (accessory for Windows XP Tablet PC Edition - due end 2002)
  .IL   Icon Library
        MSIL Assembler Input File
  .ILB  Scream Tracker Data
  .ILBM  Graphic, Sound (Interchangeable File Format) [may be .IFF file, see above]
  .ILK  MS ILink Program Format Outline
  .ILL  Adobe Illustrator Prologue
  .ILM  Satsang Quiz File
        CAS 200 QDA v3.0 Image List Mode File (DNA mapping)
        Illuminatus Opus Multimedia File
        Iomega Zip Drive Speed Configuration File [Good Info Source]
  .ILPLOPTIONS  InterLock and PowerLock (public computer management utility)
  .ILPLVOUCHERS  InterLock and PowerLock (public computer management utility)
  .ILV  ILOG View File
  .ILVG  iLiving P-to-P (iliving file viewer)
  .IM5  Visilog  [XnView]
  .IM8  Sun Raster Graphic
  .IMA  WinImage File (Floppy and disk imager)
        Mirage Vector Graphics
  .IMB  IncrediMail File
  .IMC  IncrediMail File
  .IMF  ImageForge/ImageForge Image EXE Library
        IncrediMail Letter
  .IMG  Bitmap Graphic (several programs)  [XnView] [IrfanView]
        AutoCAD CAD-Camera  [XnView]
        ERDAS IMAGINE Format
        Planetary Data System  [XnView]
        Idrisi32 Raster Image
        Radiance Scene Description Image  [XnView]
        CloneCd Related File
        Floppy Image File
        Apple Macintosh Disk Copy Format
        Microtek Eyestar  [XnView]
        Sharp GPB  [XnView]
        Starbase  [XnView]
        Vicar  [XnView]
        Vivid Ray-tracer  [XnView]
  .IMI  IncrediMail Animation
  .IMJ  JFIF File With a MS Windows BMP Header (Pegasus Image Corporation)
  .IMM  IncrediMail Trash
  .IMN  IncrediMail Notifier
  .IMP  Urban Chaos Game File
        Lotus Improv Spreadsheet
        Babya Installer Archive
        DVD File
        FileMaker Database Translation Filter
        WinIMP Archive
  .IMQ  ImageQ Presentation
  .IMR  Cognos Impromptu Report Writer
  .IMS  Incredimail Graphic
  .IMT  IMNET Image  [XnView]
  .IMV  Yahoo Instant Messenger IMVironment
  .IMW  Imageware Surfacer 3D CAD Surface Geometry
        IncrediMail Sound
  .IMY  iMelody Ringtone Format (link is PDF file)
  .IMZ  Compressed Floppy Image
        WinImage File (Floppy and disk imager)
  .IN$  HP NewWave Install File
  .IN3  Harvard Input Device Driver (Harvard Graphics taken over by Serif)
  .INB  Vermont HighText Script
        Visual Expert Source Code Documentation
  .INC  Include File (various)
        Internet Connection File (used by ISPs)
  .INCD  Adobe InCopy/InDesign Link File (Link stories from an InDesign document)
  .IND  dBase IV or DataPerfect Index
        Well of Souls Game File
  .INDD  Adobe Indesign Document
  .INF  Information or Setup File (many)
  .INFO  Amiga Information File [XnView]
  .INI  Initialization/Configuration File (many)
  .INK  Pantone Reference File
        Mimio Ink File [Electronic Whiteboard]
  .INL  MS Visual C++ Inline Function File
  .INP  Oracle Source Code
        Self-Extracting Archive Utility Project
        GIS Software Text Input File  [GIS info]
  (ArcView, et.al.) (JShape/FShape)
  .INS  Internet Communication Setting
        AdLib Instrument Music File
        WordPerfect File
        Ensoniq EPS Family Instrument
        Sample Cell / II Instrument
        InstallShield Script
        X-Internet Sign-up File
        Inspiration Mind Mapping Software File
        1st Reader Install Script
  .INSTALL  Likely a text file (e.g., README.INSTALL)
  .INT  Borland Interface Units
        Foxpro Code Page
        Signature Semi-compiled Program
        Unreal Tournament Mutator
        Intermediate Code used for syntax checking (various)
  .INTER  Interspector Project File
  .INTERLOCKFAVOURITES  InterLock and PowerLock (public computer management utility)
  .INTO  Interspector Object File
  .INU  INSPEC Configuration File
  .INX  Foxbase Index
        ACL For Windows Index (data mining software)
  .IO   Compressed Archive
  .IOB  Imagine File
        TDDD Format 3D Graphic Database
  .IOC  Instant ORGcharting! Organization Chart
  .IOCA  Image Object Content Architecture (IOCA) Graphics File  [XnView]
  .IOF  Findit Document
  .ION  Text Program/Installation Description
        4DOS File Description
  .IP   IconPackager File (changes the look of Windows icons)
  .IPD  InstallPROG 6 EDBS Install Database
  .IPF  Microsoft SMS Installer Script (with System Management Server 2.0)
  .IPG  Mindjongg Format  [XnView]
  .IPH  InterPaint Hires Image  [XnView]
  .IPK  NRG iPack File
  .IPL  Corel Pantone Spot Reference Palette
        InstallPROG 6 EDBS File Library
  .IPR  IntelliJ Project XML File
  .IPS  Game Patch File (allows running of illegal copies of some games)
  .IPT  Autodesk Inventor CAD File
        InterPaint Multicolor Image  [XnView]
  .IPW  UniPlot Graph [Free viewer]
  .IPX  Interactive Pictures Corporation AV File
  .IPZ  ICQ Skin
  .IQF  Integra 3.0 Query File
  .IQY  Excel Web Query [Buy Office XP at Shop.Microsoft]
  .IRD  MS Money Temporary File
  .IRIS  Silicon Graphics RGB  [XnView]
  .IRS  WordPerfect Resource File
  .ISD  RapidFile Dictionary
        GraphPad InStat
        InstallShield Dialog
  .ISH  Compressed Archive File
        Image Speeder  [XnView]
        Image System (HiRes)  [XnView]
  .ISK  Command File (similar to a batch file - view in text editor)
  .ISL  InstallShield Temporary Installer File
  .ISM  Image System (Multicolor)  [XnView]
  .ISO  File List for CD-ROM  [Fantom CD Emulator]
        ISO Buster File
        InstallShield Uninstall File
        ISO-9660 Table
        Easy CD Creator Disc Image
  .ISP  Internet Sign-up File
        Internet Communication Settings
  .ISR  MS Streets & Trips Route File
        Uninstaller Text File  (_deisreg.isr)
  .ISS  InstallShield Response File
        ISS Graphic  [XnView]
  .IST  Digitrakker Instrument File (by n-FaCToR)
  .ISU  InstallShield Uninstall Script
        Easy CD Creator 4 Uninstall File
        Netscape File
  .IT   Impulse Tracker Music Module
        Intalk Settings
  .ITE  E-Tabs Reader File
  .ITF  Inside Tract File
        JPI TopSpeed Pascal Interface File
  .ITG  Intergraph Format  [XnView]
  .ITH  InTether Receiver File (security software)
  .ITI  Impulse Tracker Instrument
  .ITM  Infinity Engine Game Item
  .ITS  Internet Document Set
        Impulse Tracker Sample
  .ITW  Icetips Wizard Editor (partially encrypted ini file)
  .IV   VRML File
        Open Inventor File
  .IVF  Indeo Video File
  .IVP  Truevision Targa Bitmap  [XnView]
  .IVT  Beyond 20/20 Table (Multidimensional data viewer)
        Concordance Inverted Full Text Database File
  .IVX  Beyond 20/20 Extract (Multidimensional data viewer)
  .IW   Iconware Application
        Idlewild Screensaver
  .IW4  DjVu File  [XnView]
  .IWA  IBM Writing Assistant Text
  .IWI  Ignite Image Optimiser
  .IWC  Installwatch Database (install monitor)
  .IWP  Wang Text File
  .IWR  i*write 2.0 File
  .IWR_BAK  i*write 2.0 Backup File
  .IX   Framemaker Index File
        Paperport Search File
  .IZD  Intrexx Application Export Format (binary)
  .IZT  Izl Binary Token