Can you navigate to the directory that contains ecm.exe?
You can also use "command prompt here" (this one probably only works for WinXP SP2, but it should be available for other Windows versions as well). Just install it, then right-click on the folder in the Explorer and select the resp. command from the pop-up menu.

Now, first try something like
echo 547398 | ecm.exe 100 1000
Does this work?