Windows File Associations

File associations allow the Windows operating system to "associate" specific file extensions with specific applications. This is how Windows decides which program to use to when you choose to do something with a file, like open or print it.

For example, if you are working in Microsoft Excel, and you save an Excel file, you know that the file name will be saved with an extension of .xls at the end of it.

That file extension of .xls tells Windows that the file can be opened, saved or printed (i.e., the file association is with) Microsoft Excel.

If the file has already been opened and saved with Excel, Windows XP can figure out it’s an Excel file, even if you change the file extension.

But if you receive an new Excel file from another source, say as an email attachment, and that file has another file extension, or no file extension at all, Windows may not be able to determine that the file is an Excel file. And if windows can't, the file won't open unless you change the file name to include the .xls extension. This is why it’s important to name your files with the correct file extensions.


Fixing File Association Errors in Windows XP

Windows keeps a list of file extensions and file associations within itself. You can see them by following these steps:

  1. Open Windows Explorer by right clicking on the Start button and then clicking on Explore.
  2. Click on the Tools menu, and then Folder Options.
  3. Click on the File types tab.

If a specific file association gets changed or deleted, and you try to open a file that has that extension, you will get Windows errors that say essentially "this file has no program associated with it".

In other words, if I go into the File Extensions table in Windows Explorer and I delete the association between the (fictitious) .ttt extension and the MS Word program, the next time I try to double click on a .ttt file to open it, Windows will show me this error:

File Association Error


To fix this kind of error, you choose "Select the program from a list" and click OK.

Then on the next dialog box, find the program that should be associated with the file and click on it.

File Association list


If the program you want to choose is not in the list offered, you may have to click Browse button, and browse through the C:Program Files directory for the program folder, and then within that program folder for the .exe file.

Once you have chosen the appropriate file association, make sure that you check off the box that says "Always use the selected program to open this kind of file" to make it a permanent choice when you click OK.

You can also change the program that launches when you double click on a certain file. For example, if you want all of your .txt files to open in Word instead of in Notepad, change the .txt association to launch Word instead. Here’s a step by step article that includes some steps on how to do this.

Some file extensions should not be changed. If the file has an .exe, .com or .bat extension, don’t change it. These are "executable" programs and they won’t launch if you change that extension.


Fixing File Associations in Vista

The File Associations area in Vista is kind of buried so I'm including those steps here as well.

  1. Click on the round windows button on the bottom left hand corner of your screen.
  2. Click on the Control Panel button
  3. On Control Panel, click on Programs
  4. Under Programs, click on Default Programs
  5. Under Default Programs, click on Associate a file type or protocol with a program
  6. Find the file extension you need to fix in the list presented. You may have to click in the list first and then scroll down
  7. Highlight the file extension and then click the Change Program... button on the top right
  8. Choose one of the programs recommended and then click OK.
  9. Then click Close and use the red x to close out of any other windows you opened.


Common File Extensions

Here’s a list of some common and not so common file extensions and the programs that create them:

.accdb

Office Access 2007 database file format

.accdt

Access Database Templates

.ace

Compressed file archive

.ai

Adobe Illustrator graphics

.ani

Animated cursor

.arj

Compressed file archive - ARJ archiver

.asp

ASP script or page (Active Server)

.aup

Audacity project file

.avi

Audio Video Interleave movie

.bak

Backup file

.bat

Batch file (executable)

.bc!

Bittorrent unfinished download file

.bik

BINK video file

.bin

Binary file

.bin

Macbinary II encoded file

.bmp

Bitmap graphics file

.bmp

Standard Windows Bitmap image (also OS/2)

.cab

Windows Cabinet Compressed Archive

.cbr

Comic Book Archive file or ComicBook Reader File

.cdr

CorelDRAW vector image

.cfg

Configuration files

.cr2

Canon digital camera RAW image format version 2

.crw

Canon digital camera RAW image format

.css

Cascading Style Sheets file

.ctt

Messenger Contact List

.dao

Disk at Once CD/DVD Image

.dat

Binary or text data file

.dbf

Database file

.dcr

Kodak Digital Camera Raw Image Format

.dib

Device-Independent Bitmap Graphic

.dll

Dynamic Link Library file

.dmp

Windows dump file

.doc

Microsoft Word file

.doc

Microsoft Office Word document

.docx

Microsoft Word 2007 file

.docx

Microsoft Word 2007 XML based document file format

.dot

Microsoft Word template

.dot

MS Word Document Template

.dotm

Word 2007 Macro-Enabled Template

.dotx

Microsoft Word 2007 template

.dotx

Word 2007 Template

.dwg

AutoCAD Drawing

.dxf

Drawing Exchange Format

.eps

Adobe Illustrator text and graphics (Encapsulated PostScript)

.exe

Executable file

.fil

Vault file of AVG antivirus

.fla

Adobe Flash file

.gif

GIF graphics file

.gif

Graphics interchange file format

.htm

Web page - HTML file

.html

Web page file - Hypertext Markup Language

.ico

Icon file

.ifo

DVD movie information file

.img

Bitmap Graphic (several programs)

.img

CloneCd image file

.ind

Adobe InDesign graphics document file

.jpeg

JPEG image, picture file format

.jpg

JPEG graphics file

.jpg

JPEG bitmap image file format

.mdb

Microsoft Access database

.mov

Apple QuickTime Movie file, standard Macintosh video format

.mp3

Compressed audio, music file

.mp4

MPEG-4 file format

.mpg

MPEG 1 video file format

.mpp

Microsoft Project file extension

.msi

Microsoft Windows Installer installation package file

.nrg

Nero-Burning ROM CD or DVD image file

.ods

OpenOffice org Calc Spreadsheet file

.odt

OpenOffice org Writer text document

.ost

Outlook folder file

.otf

Open type font file format

.pcd

Kodak Picture CD multiresolution Image

.pcx

PC Paintbrush Bitmap

.pdb

Palmpilot Database File

.pdf

Adobe Acrobat Portable Document File

.php

PHP script, page

.php3

PHP version 3 script file

.png

Portable (Public) Network Graphic

.potx

PowerPoint 2007 XML Template

.pps

Microsoft Powerpoint Slide Show

.pps

PowerPoint Slideshow

.ppsm

PowerPoint 2007 Macro-Enabled XML Show

.ppsx

PowerPoint 2007 XML Show

.ppt

Microsoft Powerpoint file

.ppt

PowerPoint Presentation file format

.pptx

PowerPoint 2007 Presentation

.prt

PTC Pro/Engineer Part file

.prt

SolidWorks Part file

.psd

Adobe Photoshop Document

.psd

Adobe Photoshop graphics

.psp

Paint Shop Pro image

.pst

Outlook 2003 personal folder

.pub

Microsoft Publisher file

.rss

Really Simple Syndication - RSS file format

.rtf

Rich Text Format document

.srt

Movie subtitle file format

.swf

ShockWave Flash, Animated vector format for the Internet

.sxc

OpenOffice

.sys

System file

.tif

Aldus Tagged Image File Format (TIFF) bitmap image

.tmp

Temporary file

.tmp

Temporary file

.torrent

BitTorrent information file

.ttf

TrueType Font

.txt

Common text file

.vob

MPEG-2 movie

.vxd

Microsoft Windows virtual device driver, 32 bit

.wav

WAVe PCM Sound, standard Windows sound format

.wba

WindowBlinds Desktop visual style

.wdb

Microsoft Works database

.wma

Windows Media Audio

.wmf

Windows Metafile

.wmv

Windows Media Video

.wpd

Corel WordPerfect document

.wpl

Windows Media Player Playlist

.wps

Microsoft Works document

.wri

Windows Write Document

.xls

Microsoft Excel spreadsheet file

.xls

Microsoft Office Excel spreadsheet

.xlsm

Excel 2007 XML Macro-Enabled Workbook

.xlsx

Excel 2007 XML Workbook

.xlt

Microsoft Excel spreadsheet template

.xltx

Excel 2007 file

.xml

XML document

.xpi

Firefox browser extension

.zip

Compressed ZIP archive file and compressed folder

.zix

WinZix compressed archive file



Well, I hope that helps you understand Windows file associations a little more.

Done with File Associations, take me back to Computer Tips