Hello all. I just recently acquired two imacs (27 and 21.5) at an auction. Neither of these iMacs currently have hard drives in them, but I attempted booting the snow leopard install dvd on both machines (just to test them out). Upon doing so I was unable to see anything (black screen from the beginning) but both macs chimed (as expected). So, I plugged in an old lcd into each of them and turned them on and loaded the install disk on both of them successfully (on the external lcd albeit). I am kind of lost as to what to do next, I really do not want to have to take it to an apple store and pay an exorbitant price, since I am somewhat comfortable repairing computers and there are numerous youtube tutorials for repairing imacs, but I do not know what is wrong with them or how to diagnose the problem. I have reset SMC on both, and I have taken the ram out and put it back in both of them. So what do you all think- Display?? I am (with my limited knowledge) guessing it is not the graphics card since I was able to run an external monitor. If anyone has any suggestions as to what may be the cause, and/or how I should go about fixing it, your help will be greatly appreciated.