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Some time ago I changed the way my computer reads .dat files by forcing it to always open with KM player. Now, if I save a .dat file in my laptop, its properties says that its a KMP-MPEG file. I want the type of the file to be .dat only. I have a license file that has to be in .dat format. But the software, for which I have the license file, is not able to read it. How do I change it back?

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3 Answers

It shouldn't matter what the OS says the type of file is.

As long as the file is the correct format for your software it should be able to read it.

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It says the type of the file is KMP-MPEG. –  Brahadeesh Apr 26 '11 at 22:36
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@Brahadeesh: The more you say that, the sillier you sound. –  Ignacio Vazquez-Abrams Apr 26 '11 at 22:45
    
I am sorry. But thats how it shows in its properties. right click - properties - Type of file. –  Brahadeesh Apr 27 '11 at 0:14
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If you are talking about Windows:

About "nature of file"

You have to know that the system does not read the contents of a file to classify it in registred filetypes, but only file extensions.

So, if you have a video file originally saved as .AVI, if you rename its extension to .TXT, Windows will think is is a text file. Some softwares are able to recognize filetypes by its contents, whether or not the file extension is correct (e.g. Irfanview, Media Player Classic...).

I.e, the "nature of your file" is preserved whether or not the file extension is not correct, EXCEPT when you use a repair software (or a software that try to repair a file), that could try to convert the contents of a file to the match extension format, and so it will corrupt a file that does not match current extension (for example, if you have a .JPG and rename it to .DOC, a registered program to open .DOC extension tries to recognize it as text; if you save the result, it can generate a corrupt file, no matter you change extension back to .JPG).

How to change registred filetype

Just use "open with", choose your program and mark to use always that. For .DAT files, there are a lot of programs that use them.

How about your license file

What means to read your license file?

  • If you are talking about reading a text content in it, simply open it in Notepad or Wordpad;

  • If you are talking about execute the license file to do an special thing, like registering a software that normally needs to execute a .DAT file to do it, reinstall the software that needs that license file.

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Its simply a license key. The software is not able to recognize it as a dat file. –  Brahadeesh Apr 27 '11 at 0:18
    
Then try to reinstall te software that you are using to read the license file. If it depends on Windows registered DAT filetype association, it will be fixed after reinstallation. But if the file is really corrupt (reason is above), we cannot do nothing - only acquiring a new licence file... Have you tried to read the file in Notepad or Wordpad? When you open a binary file with Notepad/Wordpad, normally the first characters identify its file content format. Could you please open the license file with Wordpad, copy and paste the first 10 characters here to see it? –  kokbira Apr 27 '11 at 0:33
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The shell settings for a file extension do not affect whether or not a file with that extension can be opened. You have other problems, such as a corrupt file.

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No. It is not corrupt. I created a notepad file and saved it as .dat. Still I am having the poblem –  Brahadeesh Apr 26 '11 at 22:38
    
did you create "a" notepad file and rename it to .DAT only to test? or was your license file created through a text you copied or written in notepad and then saved and renamed to .DAT? –  kokbira Apr 27 '11 at 0:42
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