A .data file, sometimes also called a .dat file, is a file containing pertinent information about a program or another file. You don't need a special program to read a .data file -- Notepad, Windows operating system's built-in miniature word processor, can open a .data file, and also gives you the ability to edit the file.
Click the "Start" button.
Type "Notepad" into the search bar at the bottom of the screen.
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Click on "Notepad" in the search results under "Programs." Notepad opens up.
Click "File," then "Open." Find the folder where the .data file is located, click on the file and click "Open." The .data file is now readable in Notepad.