After replacing the hard drive, the LCD lights but shows nothing.
Disk Utility indicated mechanical failure in the iMac internal hard drive: "back up everything you can." I installed a new hard drive, but when I turn on the iMac I immediately got a solid white screen.
I booted from an OSX install disk, but still got the same solid white screen.
I started it up in FireWire target disk mode, connected to a MacBookPro. Using Disk Utility on the MacBookPro, I was able to eject the OSX install disk from the iMac. I was also able to successfully install OSX Snow Leopard on the new hard drive in the iMac. But even in target disk mode, the iMac screen remains white - no blue screen with yellow target disk icon.
Now the iMac boots up fine, I hear the "Welcome to OSX" music (doot doot da do-do) but the screen is solid white.
I reset the parameter RAM 7 or 8 times. I've checked all cables inside the iMac. I booted up in safe mode and verbose mode. Always the same result - everything works, but nothing appears on the iMac screen - no spinning startup wheel, no question mark, no text in safe mode. The display lights up, but nothing appears on it.