.BAK File Extension

Backup of another document, often created automatically by the operating system or various programs such as Autodesk AutoCAD; Windows may create BAK files for the System.ini and Win.ini files.

NOTE: The file extension should be changed back to the original extension in order for the file to open correctly. This is often done by simply removing the ".bak" part of the filename. For example, "mydocument1.doc.bak" should be renamed to "mydocument1.doc" before being opened.

Backup of the Firefox bookmarks file; can be used to replace saved bookmarks in case the main bookmarks file becomes corrupted; automatically generated by the Firefox Web browser; typically named "bookmarks.bak"

The bookmarks.bak file is located in the following directories on Windows and Macintosh systems:

Windows
C:\Documents and Settings\UserName\Application Data\Mozilla\Firefox\Profiles\[randon-name]
Mac
/Users/[username]/Library/Application Support/Firefox/Profiles/[random-name].default

Backup file created by ACT!, an application used for customer relationship management (CRM); contains a backup of CRM data, which includes customer information such as names, address information, and history.

ACT! BAK files are used for restoring data in the event the CRM data is lost. They are usually created on a periodic basis and when upgrading ACT! software.