Tip: Show File Extensions

There is one very easy thing to do in Windows to make it easier to determine if a file on your computer (or coming in via email) can be potentially harmful.  And that change is to make file extensions visible.

Windows, for some inexplicable reason, hides the extensions of files by default.  Is “document” really a document?  You can’t really tell by looking at a file whether it is a picture, a text file, a song, or a potentially evil program.  With file extensions turned off there just isn’t any way to be sure.  Fortunately this is a very easy thing to fix.

In Windows Vista:

1. Click Start, type the word Folder and wait for the search results to come up.  Click on Folder Options.

2. Click the View tab, scroll down to “Hide extensions for known file types” and UNCHECK it.

3. Click OK to save the change.

In Windows XP:

1. Click Start, Control Panel, Folder Options.

2. Click the View tab, scroll down to “Hide extensions for known file types” and UNCHECK it.

3. Click OK to save the change.

With file extensions turned on and visible you will know just by glancing at an icon what type of file it really is.  And if you see something ending in .EXE, .COM, .PIF, .SCR, you will know that it is actually a program.  If one of these file types is coming to you via email, just delete it.  If you find one of these files somewhere that a program shouldn’t be (like on a USB flash drive, or your Documents folder), don’t open it.  Programs should always be stored in C:\Program Files, so if you see one somewhere else, leave it alone. 

That same folder with file extensions turned on is shown below.  We can now see that “Document” is actually an executable, not a text file!

The last extension on a file is the one that actually counts.  So if you see Cool New Song.mp3.exe, it isn’t an MP3 file; it is actually a program.  Just delete it.  Likewise with Free Gasoline.txt.exe.  You get the idea.

I’m really not sure why Microsoft insists on hiding file extensions by default.  Even the upcoming Windows 7 has this same behavior.  As poor as this decision is, at least we can change the behavior easily.