Lost power when changing computer name and key. no boot or sys disk. boots to apple logo and spin wheel. how to recover w/o loss of data

1.Try a Safe Boot
Mac OS X 10.2 and later Safe Boot includes disk checking and repair. First start your Mac in Safe Mode. To do this, shut down your Mac. Now Turn on your computer by pressing the power key while holding down the Shift key. When you see the Apple logo, release the Shift key. After your Mac fully starts, restart your computer normally without holding any keys/buttons during startup. Note that Safe Boot is slower to boot.
2.Run Disk Utility
Turn your Mac off by holding down the power button for a few seconds. Turn on your Mac and hold down the Command and R keys until you see the Apple logo. Then you should see a "Mac OS X Utilities" window. Select Disk Utility, click your OS X hard drive and select verify/repair disk.
3.Reset PRAM
This may fix your boot failure. PRAM ("parameter random-access memory") stores some of your settings. You may reset PRAM. To do that, turn off your Mac. Now turn on your Mac. Then, immediately, hold down the Option-Command-P-R keys until your Mac restarts. When your Mac is starting up, release the keys.
4.Reinstall Mac OS X
If nothing above works, you may try this. Your Mac needs to be connected to the Internet. See number#2 above. Follow the same steps. Restart your Mac and hold down the Command key and the R key until the Apple icon appears; when you see the Mac OS X utilities window, select the Reinstall option.

If you deleted all the system settings, it's hard to recovery it by no other resources. So reinstall is the only options most likely.
It depends your OS X system version to decide how to recover.
If it's below OS X 10.7, there might be a DVD disk came with your Mac computer, use that DVD disk to boot your machine to reinstall OS X. Otherwise, there should be a recovery volume could be used to boot.

To boot from DVD, take look at: "Troubleshooting Mac OS X installation from CD or DVD"<http://support.apple.com/kb/ht2956>.
Too boot from Recovery volume: OS X: About OS X Recovery <http://support.apple.com/kb/ht4718>
Here is a big picture of OS X recovery: http://www.apple.com/osx/recovery/

Or go to any Apple Store to get genus tech help.

Ref http://support.apple.com/kb/ht1533 to boot into different mode.

The time bar may be telling you that there's damage to the hard drive, or perhaps just your hard drive's main partition.
If your Mac is running OS X Lion or Mountain Lion, you should have a recovery partition with Disk Utility on it. Restart your Mac while holding down Command-R to boot into this instead of your regular partition. Follow Apple's instructions on how to use Disk Utility to see whether the hard drive is damaged or just corrupted (and potentially corrupted).

try booting with disk select option.


hold down option key and power up. Try resetting pram.


Look up key commands on apple support.


Try safe boot with holding down s key


etc....

Hi friend,

The message, "Disk boot failure" often means that the OS is corrupt and needs to be re installed. Try restarting the computer twice or thrice and check whether you can log in to the system. If the same error displays again then you have to re install the OS. But re installing the OS leads to data loss from the hard disk. So at such kind of situations you need a data recovery software to recover your data back. Yodot Hard Drive Recovery is a wonderful data recovery software which performs recovery after disk boot failure.

The windows has to be reinstalled ( Formatting the Hard Disk with DATA LOSS) Select models have the ability to have the operating system reinstalled from a hidden drive built into the computer.
To start the system recovery:

1. Restart the netbook.
2. When the Acer logo appears on the screen, press the Alt and F10 keys repeatedly.
3. If you are prompted with a Microsoft Windows boot screen, press the Enter key.
4. After the system recovery program has loaded, follow the prompts to reinstall the Operating System.
5. Select ' completely restore to factory defaults

Please boot the system with a Mac OS X installation Media .Insert the installation media and power on the system and immediately press ' C ' key to boot it from Mac OS X installation disk.After few seconds the language selection option will appear .Click continue and then in the next screen see on top you will find "UTILITY" then click "DISK UTILITY" .Select the boot drive partition and try to repair the file permissions mentioned left hand side .If the permission repaired successfully then restart the system and check if it boots.If still you face the same issue then reboot the system with installation media again and repartition the harddrive .Install the os Freshly.The issue will get solved

If you have your Mac OS X Install disc, insert it into the drive.
Restart the computer and hold down "C" while booting.
Choose your language.
Select "Disk Utility" from the "Utilities" in the menu bar.
Select your Macbook's hard drive in the left sidebar.
Click the "First Aid" tab thats along the top of the viewer window.
Click "Verify Disk" (not verify disk permissions)
If this shows errors click "Repair Disk"
Once completed close the Disk Utility window.
Restart the computer.
If this fails to fix it as well then your next option would most likely be recovering your files from the macbook either by booting into target disk mode (hold down T at startup) and transferring them via a firewire cable, or removing the hard drive and hooking it up to another Mac to get the files. Then do a clean install of Mac OS X using your installation discs.

I would try pressing f2 or f8 when first boots up, then change bios settings from first bootup device as cd rom drive, then hard disc as second drive, then place windows disc or recovery disc in pc, then reboot. and reinstall your software.

Start the computer from the installation CD, choose Disk Utility from the menu, and then choose Repair Disk with the internal HD selected. If that doesn't work, you can try a new OS installation. If your data is important, don't erase the drive during installation and select "Archive and Install" -- if your data is *NOT* important, you can just repartition the drive and install the OS.