how to block a game from functioning?, help needed... need to stop da game

hey... i need some help here.... my brother keeps playing dis game overand over again..... its and online game.!!!!... im not sure wat it is,but it is a sort of an adventure game.. MOSIANG ONLINE .... wth ... idunno wat to do... he starts at 1 in da morning... and ends at 4 in daevening...... anyone can tell me how can i block dis game withoutdeleting it, or even detected by my brother... any experts outhere...help needed..... i cant play the pc as usual alredy... its botheringme... even if it cant be stopped, any idea to make da game go worst orbeing affected....