I had problem with
ERROR [+6510] LOpen: Unable to open label file
I followd through the tutorial and also going through the htk book, but no where during the tutorial has it created any .lab files :S (wasnt it suppose to create mfc at HLEd step?) i tried reading the link u gave to another person with the same question, but i dnt get it, i did the HLEd step corret with .mfc files made and the path correct, but now its just telling me i cannot open label files which was never mentioned b4 :S
so lost...
Hi Alan,
>ERROR [+6510] LOpen: Unable to open label file
HTK is looking for the label file - which is the list of words in your text (in the order they appear in your text).
The label file is contained in your 
file (or phones.mlf). Usually when creating acoustic models, you have many transcribed
audio files. So rather than have many text label files to keep track
of, you put them all in a large single text file called an mlf file (mlf=multiple label file).
HTK assumes that the name of your label file is the same as your wav file - with the ".wav" suffix changed to ".lab". So make sure the prefix of your label file matches that of your audio file.
Ken