I also have a similar problem. Old HD was malfunctioning but imac would still turn on from time to time. I cloned a new 2TB HD from a different computer with Snow Leopard on it and swapped out the malfunctioning HD from the Imac and added more Ram. After the install I get a light, no chime and a black screen. After reading this post I had hoped that starting the the Snow Leopard install CD would fix it. Now I have a stuck Snow Leopard CD and the original problem. Should I find the original install CD that came with the Mac. If I do then how would I go about getting the Snow Leopard CD out. Please Help.