can't get past white screen

[paperhearts63]

i have a black 2008 macbook. Today i updated my itunes to the newest version and it told me to restart it to complete the update. i did and it said it showed a progress bar and said the update was finishing but when the bar was almost to the end it stopped for a long time and didn't seem to be moving, so I tried turning the laptop off then on again and now it stops on the white screen with the apple logo and the spinning wheel and won't go past it. any idea of what i can do? thanks!