Screen resolution problems

O.k my brother was fooling around on my computer and he changed my display settings. so i can no longer go on my computer in normal mode and can only enter on safe mode.

I think he changed the screen resolution to 640X480 and normal does like that. it just comes up with a black screen and some sort of error saying input range error change resolution to 1440X900.

So all i can enter is safe mode can some one help me