Archos604wifi. my archos does not let me read the files i put on it.how do i access them? i

Question

my archos does not let me read the files i put on it.how do i access them? i downloaded some files on the wifi604 archos and it wont let me read the material there.it says it cant play it ,what did i do wrong.it transfered ok,but i cant read the material i put on the wifi