Hello, I have a friend who recently upgraded from Leopard to SL on his black Macbook. After checking for updates recently, he found that he was still at version 10.6.3, and I recommended that he update to 10.6.8. After downloading the update, the Mac asked to restart the computer to finish installing the new version, as usual. Unfortunately, the laptop was running on A/C power, as the battery was completely drained. At some point during the installation, when the Mac was busy transferring the updated files around, the charger cable disconnected from the laptop, and it lost power. When my friend attempted to boot it up again, he found that the Mac would sound its start-up chime, but the Mac would hang at booting, and only display the prohibitory, or NO sign. Usually, this means that the Mac cannot find a bootable kernel or a valid set of System files to load into memory, and with the botched update, I wasn't at all surprised. So I attempted the slew of repairs, including booting to the SL install disc and running Disk Utility in order to repair the drive. The hard drive itself was reported as being undamaged, but when I tried to repair permissions, it would get within 2 minutes of finishing repairs before locking up. I tried repairing permissions this way twice, with the same results. I attempted to boot into Safe Mode, but no dice, I still got the NO sign. I tried booting into Verbose Mode, and according to the output, the Mac would load up fine, and then reach a point where it would simply loop the message, "Waiting for the disk to be ready." over and over again. I tried booting into Single User Mode, but it was just like Verbose Mode: I couldn't get the chance to enter any disk repair commands, because the Mac would simply error out waiting for the disk. I think that the only two options that remain for my friend are: 1.) Head to the Apple Store or another certified Mac repair shop and get it looked at. 2.) Let me hook it up to my Mac via firewire and enter Target Disc Mode, and recover any data that we can from it, and then just do a complete reformat and reinstall of SL. We can't install Lion on it because he only has 1GB on the laptop, and Lion requires 2GB minimum. So there you have it. Are there any other troubleshooting techniques I might have forgotten? I'm completely baffled, and I think that the SL install is hosed due to the failed update. I don't suppose there is anyway to undo the update installation, or restore the Mac to a prior point in time, like Windows' Last Known Good Configuration option, is there? Naturally, he didn't keep a Time Machine backup, so restoring from a disc image or drive backup simply isn't possible. Does anyone here have any ideas?