The cost varies depending on the destination. Windows needs file extensions in order to know what program to open for a particular file. If you do not have file extensions visible, you can identify Microsoft Word documents by their icons. With file extensions visible, you can see that Windows actually identifies word documents because they end in .doc. If the .doc were removed from the end of the file name, that file s icon would change to a white box with a Windows icon inside because Windows no longer knows what to do with the file.
Files ending in .vbs, .shs, and .exe can be very dangerous files, often containing viruses.
If you are unsure of the nature of an attachment, ask the sender what it is before opening it. It is a good idea to display file extensions so that you can see what type of files you re getting as attachments. To do that, follow the steps outlined below. Double-click on My Computer. From the View menu, choose Options.