By default, Windows Explorer shows file extensions only for files that don’t have an association with a program. That makes it awkward if you want to edit a file’s extension. To make all file extensions visible for editing in Windows XP, open Windows Explorer and choose Tools, Folder Options. In the Folder Options dialog box, click the View tab and clear the checkbox to the left of the Hide extensions for known file types option. Click OK to close the dialog box and return to Windows Explorer. You can now see and edit all extensions.
Personally, I think that option is too drastic. I don’t want to run the risk of accidentally changing a file name extension for a Word document or an executable file. But I do find it handy to show extensions for certain types of file, such as text files with the .txt extension. And it’s relatively easy to make those extensions visible. Here’s how:
- Choose Tools, Folder Options.
- Click the File Types tab and select the entry associated with the extension you want to make visible — in this example, choose the TXT extension, which is associated with the Text Document file type.
- Click the Advanced button to open the Edit File Type dialog box.
- Select the Always show extension checkbox.
- Click OK to close the Edit File Type dialog box and then click OK to close the Folder Options dialog box.
Now return to Windows Explorer and you’ll see that the .txt extension is visible (and editable) in every Explorer window.
Ed Bott 
Personally, I always leave the file extensions visible for another reason — to prevent bad guys from messing with the extensions and counting on them being hidden. E.G., if the extensions are hidden, “MyInnocentDocument.doc.vbs” displays as “MyInnocentDocument.doc”. I know that you can tell that such a file is actually VB Script by the icon (and by the “doc” extension which shouldn’t be there), but seeing the full filename is a helpful reinforcement for those times when I’m caffiene deprived…
In both Outlook and Outlook Express, the “multiple file extensions” trick has been a non-issue for years. If you receive a file attachment in either of these programs, you see the final extension regardless of your Explorer settings.
Am I the only one who is seeing squares with red Xs in the middle rather than actual screenshots?
No, Ken. I don’t see the pics either. He has them locally linked to his hard drive.
On topic, I have mine set to view the extensions. It makes it easier when renaming. Plus I always want to see the file type in case Windows cannot identify it.
I fixed the graphics. Thanks for pointing out the mistake!
Whether to show or hide file extensions is a matter of personal taste, for sure. That’s why I point out both techniques here. In Windows XP, the extension for an unknown file type is always shown, so if that’s the issue, there’s no need to change the default settings.
I install and uninstall so much software that when I come across an odd/unknown file extension, I ask, What the heck?, not having any idea it belongs to a long uninstalled program!