change default player?

hey downloaded bsplayer, like it but my gf dosent she wants windows media player as a default player, ithought that was cool. but when i open a file with WMP and tick open other files or withouth ticking, it dosent open and WMP never opens anymore at all. help please

[BSPeter]

For Windows Media Player 9:
Start it by clicking on its icon.
If menu-bar isn't displayed, switch it on.
Then select tools (or extra) > options ..... and then [filetypes]
Now check the relevant boxes and then click [OK]

(Maybe first "disconnect" BSPlayer from the file-types:
rightclick > Options > Preferences > General > File types > [Select none].)