I've just attempted to install some more DDR memory into my Compaq Presario S5600 desktop PC. To install it I had to remove the power connections for a few drives and unseat the graphics card. I reconnected everything, but when I turned the power back on there is a continuous high pitched beep, the lights come on but nothing else happens. The power connections and graphics card all appear to be correctly positioned. I also removed the new memory and I'm still receiving the same continous beep. What does this mean?