Windows Movie Maker Error!!!

Ok my problem is not the message “this file could not be imported because the codec used to play the file..." blah blah blah. I fixed that( I think so i guess)with K-Lite Full Codec
But now a new message comes up “C:\Users\Katherine\Desktop\Videos\Videos\RealPlayer Downloads\Elfen Lied - Condemned Memoir [HQ].m4v could not be imported."
is this simply because I need an update?
I mean the video caam play on Windows live but not on Windows Movie Maker. What do I do? I have a History Project soon!!!! Stick out your hand to help a poor thirteen year old !!!
lolz