if you're able to play it back, i'm assuming you've already got quicktime installed. quicktime's gay. windows media player is gay. uninstall quicktime because it's pure bloated faggotry and no different than spyware.
decoders don't take up 50+mb, call home all the time and install autostarts as a default. the free version of quicktime is aids-ridden, get rid of it.
= download VLC media player and
this which comes with media player classic.
quicktime and wmp are like skeeter kerkove and steve holmes, they impose and touch too much and they never ask and place the onus on you to tell them not to call home with tracking data about you, constantly need security updates, install taskbar nonsense, etc.