I was all set to put this "Windows Explorer Explained" series to rest for a while, but then reader Martin wrote in with a question that comes up a lot: in Windows 7, how do you reveal the hidden file extension for each filename?
File extensions (a holdover from early DOS days, believe it or not) tell you what kind of file you're looking at. Thus, a Word file has a .doc extension; a digital photo, a .jpg extension; and so on.
If you use Windows Explorer's Details view for looking at your files, you'll notice a Type column that more or less takes the guesswork out of identifying file types--and eliminates the need to see those extensions.
That said, if you want them anyway, it's an easy switch to flip:
1. Start Windows Explorer (pressing Windows-E is the fastest method).
2. Click Organize, Folder and search options.
3. Click the View tab.
4. Remove the checkmark next to Hide extensions for known file types.
5. Click OK.
Presto! Now you'll see file extensions in all Explorer views.