There are several websites out there that have the capability of converting several different file types. Maybe you have an Adobe .pdf file and you want it in Word Document .doc format. Maybe you have a Jpeg .jpg image file and what it in .png format. Or maybe you have an audio file that is in a format where you do not have a program to play it or the program costs money to play the odd format. You can easily convert many different types of audio files to .mp3 which is the most prevalent audio format today.

Follow up:

Zamzar.com

offers to convert the following file formats for free:

Document formats

csv - Comma Separated Values
doc - Microsoft Word Document
docx - Microsoft Word 2007 Document
odp - OpenDocument presentation
ods - OpenDocument spreadsheet
odt - OpenDocument Text Document
pdf - Portable Document Format
ppt - Microsoft PowerPoint Presentation
pptx - Microsoft PowerPoint 2007 Presentation
ps - Postscript document
pub - Microsoft Publisher
rtf - Rich Text Format
wpd - Wordperfect Document
wps - Microsoft Works Document
xls - Microsoft Excel Spreadsheet
xlsx - Microsoft Excel 2007 Spreadsheet

Image formats

bmp - Windows bitmap
gif - Compuserve graphics interchange
jpg - JPEG compliant image
pcx - PC Paintbrush Bitmap Graphic
png - Portable Network Graphic
tga - Truevision Targa Graphic
tiff - Tagged image file format
wbmp - Wireless Bitmap File Format

Music formats

aac - Advanced Audio Coding File
ac3 - AC3 Audio File
flac - Free Lossless Audio Codec
m4a - Compressed video file
mp3 - Compressed audio file
ra - RealMedia Streaming Media
ram - RealMedia Metafile
wav - Windows audio file
wma - Windows media file

Video formats

3g2 - 3GPP2 Multimedia File
3gp - 3GPP Multimedia File
avi - Windows video file
flv - Flash video
gvi - Google video file
m4v - MPEG-4 Video File
mov - Apple QuickTime Movie
mp4 - MPEG-4 Video File
mpg - Moving Picture Experts Group File
rm - RealMedia Streaming Media
rmvb - RealVideo Variable Bit Rate File
vob - DVD Video Movie File
wmv - Windows Media Video

Compressed formats

7z - 7-Zip Compressed File
tar.bz2 - Bzip 2 UNIX Compressed File
cab - Cabinet File
lzh - Compressed Archive File
rar - WinRAR Compressed Archive
tar - Tape Archive File
tar.gzh - Gzip Compressed Archive
yz1 - DeepFreezer Compressed Archive
zip - Compressed Archive File

Here is a list of the different file types and what they can each convert to:

http://www.zamzar.com/conversionTypes.php

For example, you can convert a .docx file - Microsoft Word 2007 Document to any of these formats:

doc - Microsoft Word Document
odt - OpenDocument Text Document
pcx - Paintbrush Bitmap Image
pdf - Portable Document Format
png - Portable Network Graphic
ps - Postscript document
txt - Text document

Sometimes we can get files from people but don't want to get the program that they use to open them so luckily we can easily just change the file format online.

There are several other websites available here:

http://www.youconvertit.com
http://www.mediaconverter.org/
Free Online PDF Creator - http://online.primopdf.com/