How do I change a core error message? I would like to change the default error message from Drupal core.

The error message is "Please Select the Valid File Format".

My problem is in brief below.


I have created a CCK called 'Assignment'.
There I have given the users an option to upload files.    
In such case if the user uploads invalid file format drupal will throw the error message as mentioned above.   
I need to change the error message in to "The file upload field cannot upload the speicified filed".


How can I achieve this?

(Should not use string overrides module)

Thanks in advance..
If that string is run through the t() function (which is probably is) and you don't want to use  String Overrides, then you can update your settings file.

For Drupal 6, putting this in your "settings.php" file should work.

$conf["locale_custom_strings_en"] = array(
  "Please Select the Valid File Format" =&gt; "The file upload field cannot upload the speicified filed",
);


In Drupal 7, you would change it to 

$conf["locale_custom_strings_en"][""] = array(
  "Please Select the Valid File Format" =&gt; "The file upload field cannot upload the speicified filed",
);


However, I am not seeing the string "Please Select the Valid File Format" in any of my D6 installs, and that is not the message I get when try to upload to a CCK filefield with the wrong file type or the MIME type doesn't match the file extension.