iBook Help PLEASE

For about the last month, I have been having troubles with my ibook G4. I turn it on, and am either greeted with a blank screen OR the Apple Screen with the loading wheel (which never leads anywhere). On top of this, There is a almost a screaming sound that comes on right when I boot up the iBook, does anyone know what the problem could be!?

So it will never load up the OS? Have you tried re-installing the OS? Running the disk utility?