How to Restore a .BAK Fileby Greyson Ferguson ; Updated September 28, 2017
Many computer programs automatically create backup files of important files being used. These are .BAK (backup) files. The .BAK files can be for anything from a Word document to a saved game or even system files. The good thing about restoring a .BAK file is that no additional software is required. Only the program that uses the original file will be needed.
Open "My Computer."
Navigate to the specific .BAK file you want to restore.
Right-click the file and choose "Rename." Only change the file extension and not the actual name. Change the file extension back to the original one. For example, if "untitled.bak" is a backup for the Microsoft Word file "untitled.doc," then just replace the ".bak" with ".doc" (note that if the original file still exists, you may have to change its title too, because you will not be allowed to have two files of the exact same name saved in the same location).
Double-click the newly renamed file. The program will now be opened.