A Comma Separated Value (CSV) file is a text file that contains data values separated by commas. A BAK file is a backup file created by any number of applications. The BAK file type is a generic file type. However, if the BAK file is saved in text file format, and the data in the file is comma separated value (CSV) data, changing a BAK file to a CSV file is as simple as changing the file extension. Note that the BAK file may not be in CSV format. In this case, changing the file extension will simply show the file in ASCII (text) format.
Click the Windows "Start" button, and click "Open Explorer" to open Windows Explorer.
Click the "Tools" option on the top navigation bar in Windows Explorer, and click "Folder Options." The Folder Options dialogue box opens.
Click the "View" tab, then uncheck the "Hide Extensions for Known File Types" option. Click "OK." The file names are now displayed with the file extension.
Right-click the "BAK file, and click "Rename." The file name, along with the extension, is highlighted.
Select only the file extension (".bak") segment of the file name and replace the extension with ".csv" by typing the characters over the highlighted file extension. A confirmation dialogue box opens.
Click "Yes" to confirm the Rename operation. The file extension is now changed to CSV.
Right-click on the CSV file, then click "Open With."
Click the "Microsoft Excel" (or other spreadsheet) option. CSV files may be opened with a spreadsheet program or with a text editor such as Windows Notepad.