Backup file created by Microsoft Word, a popular word processor; contains a backup copy of a Word document (.DOC); used to recover a document file in the event that it is deleted or corrupted.
WBK backup files are automatically created when the "Always create backup copy" option is enabled in Word. You may enable this option in Word 2003 by navigating to Tools → Options → Save. In Word 2007, select Word Options → Advanced from the Microsoft Office Button.
NOTE: If a WBK file is not found on your system, there may also be an auto-save file (.ASD) that can recover the Word document.