How do i change the program that opens videos?

Every time I open a video, quicktime player opens it, but I can%26#039;t play it on windows media player. It says on the properties list that it should play on windows, but i always get an error code. what do I do?|||Right-click on the file, choose Open with ..., select program from list, then either pick a listed program or use the browse button to select the program you want to use. Check on the box that asks if you always want to use that program for this type of file, click OK.