Disk cannot be repaired, Incorrect Block Count, Invalid Node Structure

I've experienced the above error messages recently on my 2006 Intel iMac running Snow Leopard 10.6.8, after several shutdowns [power failures]. My Mac's response was a no-start [grey screen, spinning gear, loading bar that never finishes. It would attempt to boot 2x then shut down abruptly w/ a black screen.]

I have always been able to successfully boot it by using my ORIGINAL Tiger 10.4.7 install disk and choosing Disk Utility. Here are the steps I follow;

1] Unplug AC power for 30 seconds then hold power button to dissipate reserve voltage. [Never works on it's own, but I always try it].

2] Disconnect all peripherals [ I use a Bluetooth KB and mouse.]

3] Insert ORIGINAL Tiger install disk. [An image of it may work. I never tried it because I have my factory disc. I believe you can make one, and only one copy of it.]

4] I use the 'option' key to boot to the CD. ['C' key never works for me.]

5] Have patience, let the install disk load, connect w/ Bluetooth [if necessary], choose language, etc...

6] Choose Utilities> Disk Utility

7] Choose your problem Mac start-up Volume from the list @ left. [In my case it's always my internal Hard Disk Drive]

8] Choose 'Repair Disk'

9] Ignore the results. You'll likely see error messages including; 'Incorrect Block count', 'Invalid Node Structure', 'This Disk needs to be repaired', 'This Disk cannot be verified completely' etc... Don't believe it- entirely.

10] Quit 'Disk Utility' and choose 'Restart'.

11] Eject CD by depressing mouse upon start-up. [The keyboard eject key never works for me.]

12] Allow your Mac to start from your normal [problem] start-up volume. I think it's automatic, but if you have a choice, make it.

Mine always starts w/ all info completely intact and accessible. I'm sure it has not been completely 'repaired', because a proper [or improper] 'Shutdown' or 'Restart' will likely force me to repeat the above steps.

I've spent the time to write this to convey my most important point; Even though Disk Utility reports an unsuccessful repair on an unmounted disk, it may not be true- so don't quit there. Why does that matter? Because if you can boot to your problem disk, you have many choices to copy, save, or otherwise back-up your valuable info to another storage medium.

My "unrepairable disk/ volume" has undergone the above procedure about 3x in 3 days due to improper shutdowns. That was more than 2 wks. ago. I haven't allowed it to restart or shutdown since. Improper ones are outta my control. I'm not worried though, because upon the 1st good boot I ran a thorough back-up. I'll add my observation that my Mac works as good and fast as it always has.

I'll have to fix it "for real" soon. I don't have to rush because I've saved everything I care about.

For those of you who may be thinking of HDD failure or HDD too full, I can only provide these facts;

1] I replaced my original HDD 6/11/10.

2] The current one passes all tests I have... R/W, SMART, Surface Scan, Errors, etc...

3] I thought it might be too full since I had less than 10% free space. I corrected that upon my 1st good boot to about 17% [216 GB tl., 37 GB free]. Though not the best, it's the best I can do and it exceeds the suggested 15% guidelines.

Lastly, I wrote this in order to give something back. I've learned so much from this forum and so many others. I've gotten so wrapped up in solving my own problems and others have provided answers for me. I was way overdue to share something significant w/ others looking for answers.