i have a file in .mov format and when i tried using TMPGEnc, it said that the file was not supported. but i have converted a .mov file into a .mpg before but for this file it doesn't work, why not?

i have another file that is in .wmv and when i try to converter it to .mpg, the program stops working. i have tried renaming the extention from .wmv. to .asf but the result is the same.

can anyone help me with this? thanks.