Help! My MacBook Pro (Mid 2009) will not load!

My MacBook Pro will turn on and off. When I turn it on, I hear the chime and the fan, but all I see is the Apple logo with the loading circle. It stays on that screen forever and sometimes a "no symbol" (circle with line through it) will come up. It just started doing this one day. I opened my computer after it was asleep, and my log in box never popped up for me to type my password in. So I turned it off and this problem started when I turned it on. what is wrong and is there anything I can do to fix it?