Re: Hello! I have the Acrobat XI test version installed, got the registration Mail and confirmed it. When i have the program opened and try to convert the file from a pdf to a word and press the convert button, it shows a the message "application failed"

You need to open that document in Acrobat, not Adobe Reader.

To do that automatically, open Adobe Reader or Acrobat: Edit | Preferences | General, then use the Select Default PDF Handler button to specify which software should open a PDF.