I just purchased a Sony Vaio Pentium 4 PCV-RX550 desktop computer, when I turned the power on, the monitor screenn is all black. The monitor is a brand new working one, so it should not be the problem with the monitor. I tried to remove the RAM and the motherboard starts beeping, so may not be the problem with the motherboard. After I put the ram back in, the screen is still black, can someone tell me what's wrong with it? Any suggestion is greately appreciated!