SUMMARY: To help prevent against opening rogue files with double extensions, enable viewing file extensions from Explorer.
By default, Windows 7 hides the file extensions of known file types in Explorer views. The reasoning - this keeps the display clean, as often a file's icon signifies its type.
However, as in in Windows Vista and earlier, this default setting is a potential security risk. It's possible that you can receive a file via e-mail with an extension of ".txt", or a file with a Notepad icon. Unfortunately, this file could have a hidden second extension, meaning that if you double-click the file, you may actually execute spyware or other malware instead!
Don't just take my word for it - Anti-virus and security software developer F-Secure describes this problem as well in their blog.
Luckily, the "fix" for this is easy:
1. Click the "Start" button, type folder options and click the "Folder Options" link that appears.
2. When the "Folder Options" multi-tabbed dialog box appears, click the "View" tab.
3. Uncheck "Hide extensions for known file types".
4. Click "OK" to close the dialog box.
Return to the Windows 7 page.
The MalekTips website was created in 1998 by Andrew Malek of Envision Programming. The page's goal is to freely disperse computer-related tips, hints, and informative articles. Tips are organized to be easy to find, and are presented clearly, in easy-to-understand language.