No in-game sounds - please help!

Question

Hi there,
I am a bit of a n00b to C# and I have been building a few of the games on this site. The problem is though, that hardly any of the sounds work on my computer.
For example, in the BrickOut game, then I'm playing the game, the only sound that seems to work is the 'WallHit.wav' file. And in SpaceInvaders, none of the sounds work. All the files seem to be '*.wav' and they ALL work when i play them through MediaPlayer.
Any ideas what the problem could be, I'm at a total loss? :(
Thanks,
Nick