I have a mid-2007 iMac, 2.4Ghz, 2GB RAM, with an ATI 2600 pro. When I press the power button, it would chime and boot up but there was no video output from both the internal LCD and an external monitor. When I connected via screen sharing and opened System Profiler, nothing showed up under Graphics/Displays. When I opened it up to look at the diagnostic LEDs, the #4 LED was off or would flicker (the flickering only happened once). After doing some research I bought a used graphics card, and when I installed it, it wouldn't chime at all. I can hear the hard drive spin up and then the fans start spinning at the maximum RPM. Diagnostic LED #4 still stayed off. I tried resetting the SMC but it didn't help. If I remove the graphics card it boots normally. Is this new graphics card bad or is it something else?