Have you opened the computer to make sure fans are all moving? Also hard drive could have died. As the sounds you describe are either coming from a fan or the hard drive.
Unplug the computer, press and hold power button for 5-10 seconds till all lights go off. Then plug it back in and try turning it on. Count the seconds it stays on before it shuts off. Im guessing it will be around 2-5 seconds.
There is a point in wisdom and knowledge that when you reach it, you exceed what is considered possible - Jason Schoon