File extensions are the letters following the last period in a file name. They typically instruct the computer as to what the purpose of the file is, and what program is used to open the file.

By default, modern versions of the Windows operating system turn the extensions off, which can be problematic for some users.

To turn file extensions on, perform the following steps (this works in all versions of windows):

• Open My Computer
• Click Tools in the menu bar
• Click Folder options
• Click the View tab
• Scroll down until you find "Hide extensions for known file types" and UN CHECK the box.
• Click OK

If you are having trouble following these steps, do an internet search on revealing file extensions in windows and follow the steps of a trustworthy set of instructions.