Consider the case when the Mac HD is almost inaccessible to the user, raising pool of serious concern over the integrity of data & hard drive. Astonishing cases had been reported in the past where a Mac HD failed to appear in Disk Utility but surprisingly shows up when attached to a PC. Although on PC too the HD appears with little or no credentials.
However, the windows system let us examine the hard drive in a peculiar fashion, making everything on the hard drive almost locked & a right-click of the mouse ends up displaying 'HELP' options & all others as inactive (Grey colored). It's obvious that PC won't read/write the Mac formatted hard drive but at least it let us know that drive is not completely dead and may require a repair.
Below are some points to repair/recover hard drive & data…
Run Disk utility: Use the Mac OS X Installation disk to boot the Mac & select your language to move to the main OS X screen. Using Utilities launch disk utility to verify & repair disk permissions. This might cure minor faults on the hard drive but won't be helpful for major faults. Bingo, if this works out otherwise there have to be other procedure soon to be followed.
Clone Mac HD: What if there exists No Startup-Disk, No Boot?
Too much extent the Mac will be unbootable due to lack of required boot disk, until you create a clone DVD of your boot volume. The clone of the Macintosh HD to an external media (supposedly a hard drive) with the help of Stellar Drive Clone can make you open disk utility from the cloned hard drive media and troubleshoot your Mac.
Another superb method to boot a Mac without an Installation disk is the use of a great utility called 'AppleJack'. With the help of few command lines, Applejack software will enable the user to perform basic system maintenance tasks when Mac doesn't even boot. This utility is most suited for PPC & OS X up to 10.6 through which disks repairs, permission repairs, caches could be managed. And, also it's a free utility to have on your Mac OS X. An example of Applejack command line would be: -
You can repeat until the utility says 'Your file-system is good'.
Data Recovery through boot disk: There is good number of data recovery software available to a user that brings in Boot DVD with them. If you lack any installation/boot DVD, then don’t worry, you might get it from the data recovery software vendor. Once data gets off from the troubled HD, save it to a safe location & now you can switch to repair the Mac hard drive with the help of a volume repair.
Screen-shot: Files ready for recovery on an unmounted hard drive using Mac recovery software.
Target a Mac: Firewire cable makes two Macs (hard drives) and even Mac - PC drives connect & share each other data. Though their exists few tools that can read Mac hard drives on a Windows system, it hardly makes any sense to access the files. Macs in target disk mode would facilitate as source & destination devices with the bad hard drive as source & healthy Mac as destination.
If every other attempt failed on the Mac HD & seems like none of the recovery & volume repair tool would be of much help then take the HD to the nearest Apple care.