The hard drive on my 24" iMac died a few weeks ago, and I was able to get a new one installed (no Apple Care) on my own. I inserted the OS X (Snow Leopard) DVD that came with the iMac, so I can install the OS. I hold down the "C" key when I press the power button (I've also tried holding down the Command key) and the iMac reads the CD for a few minutes, then the screen fades out to a dark gray, with the following message (see attached photo): "You need to restart your computer. Hold down the power button until it turns off, then press the power button again." I've gone though this process about 4 times, and each time the same error message displays on screen. Any ideas what's going on here? Thanks much in advance.