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SOLVED FF 19. What to Do? URL Link, ascm could not be opened, the associated helper application does not exist. Change the association in your preferences.

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The error message above appears when I try to download an e-book file with the extension .acsm I have read many posts. At mozillaline site (? from 2008) http://kb.mozillazine.org/The_associated_helper_application_does_not_exist

Firefox 2: Tools -> Options -> Content / File Types -> Manage  (There are no File Types or Manage)

Firefox 3: Tools -> Options -> Applications (There is no ascm file or program to change, and no way to add to list) I tried http://kb.mozillazine.org/MimeTypes.rdf mimeTypes.rdf is a file in the profile folder. mimeTypes.rdf stores information about which action is to be performed when downloading certain types of files, such as opening the file in a specific program or saving it to disk. In Firefox, this information can be viewed or changed in "Tools -> Options -> Content / File Types -> Manage..." (There are no File Types or Manage and there is no method to Add)

The acsm extension is a common e-book file. I use Kobo Books.

The error message above appears when I try to download an e-book file with the extension .acsm I have read many posts. At mozillaline site (? from 2008) http://kb.mozillazine.org/The_associated_helper_application_does_not_exist Firefox 2: Tools -> Options -> Content / File Types -> Manage (There are no File Types or Manage) Firefox 3: Tools -> Options -> Applications (There is no ascm file or program to change, and no way to add to list) I tried http://kb.mozillazine.org/MimeTypes.rdf mimeTypes.rdf is a file in the profile folder. mimeTypes.rdf stores information about which action is to be performed when downloading certain types of files, such as opening the file in a specific program or saving it to disk. In Firefox, this information can be viewed or changed in "Tools -> Options -> Content / File Types -> Manage..." (There are no File Types or Manage and there is no method to Add) The acsm extension is a common e-book file. I use Kobo Books.

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Usually if Firefox encounters an unrecognized type it will present Open/Save/Cancel dialog.

You might want to try renaming your mimeTypes.rdf file in case a plugin you removed is still listed in the file as a handler for that content type. Firefox will use a default file when it restarts.

Open your current Firefox settings (AKA Firefox profile) folder using

Help > Troubleshooting Information > "Show Folder" button

Switch back to Firefox and Exit

Pause while Firefox finishes its cleanup, then rename mimeTypes.rdf to something like mimeTypes.old

Restart Firefox. Does it behave better?

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Thank you for your reply. Your advice was spot on regarding the solution to my problem.

I followed your advice and was able to purchase a book and download it via the dialogue box. I saved it and moved it to my e-reader.

I have a related question. The size of the original mimeTypes.rdf is 18KB, whereas the new mimeTypes,rdf is 5 KB. Why is this so and should I be concerned?

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The mimeTypes.rdf file tends to accumulate entries over time. I think if Firefox doesn't find the answer in the smaller file, it will prompt you for information. I doubt that anything essential is missing. In theory, you could compare the files (for example, using WinMerge), but the format is not very self-explanatory, so I don't suggest trying to manually copy over any entries.

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Thanks for your information. I have marked this post as SOLVED.