File extensions are those 3 or 4 little letters after the dot which tell Windows what type of file it is. For example:
- report.xls is an Excel spreadsheet (.xls)
- report.doc is a Word document (.doc)
- report.exe is a program (.exe)
By default, file extensions for known file types are hidden in Windows operating systems. In my view this is both stupid and dangerous. Stupid because we need to see what type of file we have in front of us. Dangerous because double clicking report.exe doesn’t open Word, it opens the file as a program which could potentially be a virus. You can however change this setting so that file extensions are shown for files in a certain folder or for all files on your hard disk.
To show file extensions in Windows XP
Open “My Computer”, select “Tools” then “Folder Options…”
In Advanced Settings, untick “Hide extensions for known file types.”
To show file extensions in Windows Vista or Windows 7
Open Computer from the Start menu
Click the Layout button (to the left of the Views button)
Click Folder Options
Click the View tab
Untick Hide extensions for known file types
This setting will make file extensions appear in all folders in both XP , Vista and Windows 7.
If you want to hide file extensions at a later time, you can tick the box again then click OK. I’d recommend that you leave it like this as it is far safer and easier to show them.