File extensions are those three (or four) letters after the period in a filename. Chances are, Windows is hiding them from you, as is the default for Windows Vista and 7.

But you’d really like to see them! For example, you’d like to know which is an old Microsoft Word .DOC file and which is a new .DOCX file. You’d like to know if you saved that new webpage as .html or accidentally did .html.txt (which is really easy to do in Notepad if you’re not careful). You recently converted a movie for use on your tablet, but you’re not sure whether you’re looking at the original or the conversion.

All of these are good reasons to turn extensions back on. There’s really no reason not to.

To do this, click Start, then Control Panel, then Folder Options. Click the View tab, then deselect Hide Extensions for Known File Types.

You XP users don’t need to perform this, as you get to see extensions from the start. Lucky you!