Mac Mini won't boot and won't fix

"I don't have a good answer for why your mini isn't booting from either the internal drive or the CD, but for recovering your data you might try using Target Disk Mode.

If you're not familiar with Target Disk Mode, shutdown the mini, plug it into another mac via a firewire cable, turn on the mini and immediately hold down the T key on the keyboard. If all has worked correctly, you'll see a blue background and a yellow firewire icon on the mini's screen. At this point the mini will be mounted as a hard drive (and just as a hard drive, the OS on the mini hasn't even booted fully) on the computer you've hooked it to. As long as your hard drive isn't failing, you should be able to read and write data to it from there. Check this support document for more details.

Once you've recovered all your critical data, you might experiment with erasing/reformatting the drive while its connected via the Target Disk Mode and see if that fixes your problem. I suspect that doing so won't fix your problem, given the symptoms you've described, but its worth a shot."

"If the Mac is ejecting the Boot DVD/CDROM after a few moments, then it's not the right disk (or the disk is damaged). The Power PC Mac Mini requires a minimum OS of 10.3.7, and should work with anything from 10.3.8 or higher (Maximium is 10.5.x).

If it's rejected immediately, then it's a Media Read error... Try examining the disk, and/or cleaning it.

Otherwise, target disk mode is your best chance..."