System crash, power surges, and system freeze are some common situations, which cause improper system shutdown. In Mac OS X machine, you need to hold the power button to reboot your system improperly when it crashes or stops responding. In a few cases, your system may boot properly after unexpected system shutdown. However, under some situations, it may refuse to boot up and give you some error messages related to missing/corrupt system files. In such situations, you can not get into your Mac machine to access your valuable data from it. This behavior leads to severe data loss and requires Mac data recovery to be fixed, if there is no backup in place.

You may face any of the below behaviors after turning your Mac computer off, improperly:

You see a blank blue or gray screen when you repeatedly try to reboot your system after shutting it down incorrectly.

You can get into the Disk Utility through boot DVD of Mac OS X 10.5 Leopard operating system, when you attach a new keyboard to your system, but can not repair or verify the hard drive...