I have a file that I need to open for educational purposes, but Windows will not let me open it. It says that the file is unknown.

Windows and Unknown File Types

With thousands of file types in existence, it's not unusual for Windows to come across unknown file types or to generate an error message when your computer doesn't have the right program for a known file type. It's also not unusual for Windows to lose its file associations and become confused over which program it should use. In your case, the first step is going to be to determine what type of file the file is, whether your computer has the right program for opening the file, and, if not, where to find a compatible program.

Determining the File Type

Your computer may not be set to show you the file extension by default, so you may need to go into Windows Explorer and make a minor setting adjustment. Go to Windows Explorer (right-click Start and choose Explore). Click Organize > Folder and Search Options > View. Scroll down and remove the checkmark in the box labeled "Hide file extensions for known file types" and click OK.

Next, navigate to the file that you are trying to open. What is its file extension? You can also right-click the file and choose Properties. The General tab will display more information about the file as well as provide you with a way to easily change the program that is set to open it. For example, if you see that the file is a .doc file and that Microsoft Word is no longer set to open the file, you can click the Opens With "Change" button and reset the file association so that Windows recognizes the file as a Word .doc document and launches Word to open it.

Once you determine the file extension, go to the Filetonic File Extension Library and look it up. For example, if the file ends with the file extension .dmg, you'd learn that this file extension is a disk imaging file for the Macintosh platform and that your computer would need a specific program, such as UltraISO or ISO Buster, in order to open the file.  

Locating the Correct Program

Now that you know the file type and its associated programs, you'll need to see if your computer is equipped with the right program. Some files can be opened by multiple programs. For example, .rtf files are text files that can be opened in virtually any word processor including the built-in Notepad. Others need specific programs or viewers. Others still may need to be converted into a compatible format. Figuring out the correct program goes back to determining the file type. Once you know that, you can search online for the right program.

Celeste Stewart | May 17th, 2010
Tags: Determining File Types, open file, unrecognized file
Categories: File Extensions

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