My Dimension E521 won't work. When I turn on the power, the monitor stays blank (if I turn the monitor on, the screen's power light stays orange and never turns green like its suposed to when the computer's power is on), the optical mouse and keyboard's lights don't come on, and while the tower's light does come on and boot-up, the fan in the tower gets extremely loud. Originally, the fan was so quite, you couldn't hear it. Now it gets so loud, louder and louder, that I can hear it from outside the room. What could it be and what can I do?