Can't open it

Hello,
i am new at this and i had 321 media player classic on my windows vista, to open video some clips when friends send them in there emails to me, now it won't open... microsoft comes up and it says microsoft have stopped working and it will let me know if there is a soultion.. but no one lets me know and i can't open the video clips.. please help this is so hard for a senior.. its hard teaching an old dog new tricks..