How can I show hidden file extensions in Windows?

Q I sent my PC to a repair shop for some maintenance and to have a new hard disk fitted. Now it has returned, I keep seeing a warning whenever I try to rename photos in Windows XP.

The error message warns that renaming a file could make it unusable. If I do rename the file I can no longer open it. Why is this happening?
Malcolm Whiteley

A It sounds as if the engineers may have adjusted a few settings on your computer after installing the hard disk but this is nothing to worry about. This is quite a simple change that can be easily reversed.

Filenames can be listed in their entirety, like Filename.jpg for example, or Windows can hide the file extension (the last three letters after the dot in the filename). In this case the same file would be listed as Filename.

When you double-click on a file, Windows looks at the file extension to help it decide what program the file should be opened with. It sounds as if your original setting was to hide the file extensions, but the engineers have made them visible again.

To change this, click on the Start menu then click on My Computer to open Windows Explorer. Click the Tools menu and click Folder Options. Click on the View tab, then scroll down to the option Hide extensions for known File Types. Tick the box next to it and click OK.

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