Sometimes you may come across unknown files on your computer. They may be found by accident when you are cleaning up your folders or Desktop. Often someone emails you a file that you can't identify. It can be difficult for Windows to open a file if it can't tell what program created it. Here are some things you can try to identify and open mystery files.
Step1
Get more information about the file from the person who sent it to you. If you need a program that you don't currently have to open the file, download it from the software manufacturer's website. Step2
Open various programs installed on your computer, especially ones that you don't use very often. Go to "File" and select "Open" from the menu. If there is a box at the bottom of the window specifying the file type, change it to "All Files." Browse to the mystery file and try to open it. If you get an error message, hit "Cancel." Step3
Right-click on the filename. Select "Open With." Select "Choose Program." Browse to "Notepad." If the file is text based, it should open in Notepad. If not, try a graphics program, like Windows Paint, and a media program, like Windows Media Player. Step4
Send the file to a friend who has a different operating system than you, like Unix or Mac. Ask your friend to try to open it. Step5
Open your Internet browser. Go to a search engine like Google or Yahoo. Type in the file's extension (the three or four letters at the end of the filename after the period). Follow links in the search results to try to figure out what type of file it is. Step6
Go to the "WhatIsThatFile" or "Filext" website. Type in the file's extension in the search box. 
