This is an area all about "codecs" and add ons. Rather than spend more than a minute learning all this, why not go get VLC PLAYER and play?
My wife and I both have laptops. We both work from the same home network. We both have win 7 with Win Media Player. hers, a samsung 580, will not play an .iso file, though it be newer than mine, ASUS k501. and mine will play the .iso files