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I have a black screen on my iMac 20" mid-2007. What happened was that I just installed windows 7 professional on the partition which works fine. Then, I tried to install the driver from a disk which comes with the windows 7 installer. After I started the installation process, the screen suddenly went black and I got a message on a small yellow background that says “error…” and then it went completely black. I tried resetting the PRAM and doing other basic troubleshooting but all to no avail. I opened it up, and I found out three lights on the motherboard (counting from the left) are ON but the fourth light is OFF. When I turn it on, the fan works, the DVD drive works too but No startup chime, no display (all blacked out). I tried troobleshooting the screen first by connecting to external display, but I got no display on the external screen. I read something online that says it might be the logic board and I bought a new logic board, the results are still the same with the old logic board. I really need help to figure this out. PLEASE HELP.
First hook it up to an external monitor to see if it is generating a video signal. In my experience, what fails on this model is the inverter: iMac Intel 20" EMC 2133 and 2210 Inverter Replacement
