Display File Extensions in Windows Explorer and Dialog Boxes
With the way that Windows is designed, file extensions can be tagged to a program. Let's use CorelDRAW files with CDR as their file extension. Each the files will display "CorelDRAW X6 Graphic" if CorelDRAW X6 was the last installed version. Many users make the false assumption that the file is truly saved as a CorelDRAW X6 file. Any file with the CDR extension would be labeled as a CorelDRAW X6 file and it may not be a CorelDRAW file at all. I could easily rename a text file with the CDR extension. Even if it is a CorelDRAW file, it could have been created in any version and still it would be labeled as a CorelDRAW X6 file.
One way that malware authors trick users is by relying on the users having file extensions hidden. They will label a file with something that appears to be a JPG extension when in reality it is an EXE file that will damage your system when run.
In short, I believe all users need to have the file extensions displayed rather than the default of having them hidden. It is one of the first changes I make to any new system I get. To start the process, you need to open "My Computer" for XP users or simply "Computer" for Vista and Windows 7 users. Windows XP users would then select Tools | Folder Options from the menus. Vista and Windows 7 users will select Organize | Folder and Search Options. Once the dialog box has opened, it is nearly identical on all operating systems. Go to the View tab and make sure there is not a checkmark in "Hide extensions for known file types" as shown highlighted above right in the dialog box. While in the dialog box, you may find other settings you want to change. When done, click Apply. Now you'll see the file extensions in every place that shows file names.