Go to the one of the files you want to open and right
click on it.  When the box opens choose "open with"  it
will then give you a choice of windows media, real player
or choose program.  Select "choose program" find the
widows media player in the box  select it and check mark
the box that says "always use this program to open these
files" this should make your media player the default
player and change them to use media player.  Then you have
to go into Real Player and go to prefrences.  Under
prefreces go to content/media types and deselect all
including the box at the bottom.  This should remove real
player as your default player.  Restart your computer and
real player will ask you to be the default player select
no.  Hope this helps