I ve compaq notebook wih windows vista,i installd yahoomessenger..but its not opening...y?can u guide me .?

i installd 3 times yahoo messenger in my notebook,but its the same..not opening. i can open yahoo...and check mail....no problm..and i open..msn too..so i request u to send dme the ..right way..how can i use yahoo messenger in my note book.compaq ,v6000,,windows vista basic.