Hi, I've just installed an additional hard drive (500gB) into my G5 computer (it had 80gb) along with an addtional 2gb ram (it only had 768mB). When I start the computer, it starts up though I don't get any response from the monitor. The light on the front of the machine flashes brighter every 5 seconds. I've tried removing the newly installed HD and ram but it just does the same thing.... what have I done wrong?