Desktops :: Disk Repair - Volume Structure Failed

I have recently purchased an iMac (21.5" - 3.06 GHz Intel Core 2 Duo - 4 GB 1067 MHz RAM - 1 TB harddrive) with OS X 10.6.2 installed. I have to say that after over 20 years with MicroSoft I am enjoying the stability and quality of the MAC. Anyway, as part of my education in the care and feeding of a MAC I ran the TechTool app yesterday. I had no indication that anything was wrong with the computer - but, I would like to become familiar with the various utilities for the care of the machine "before" a problem occurs. As the app ran I was pleased to see that all the tests passed (Processor, RAM, Video RAM, etc.). However the computer failed the last test: Volume Structure.

Here are the directions I was given at the end of the test: Volume Structure Failed
TechTool Deluxe can scan volumes for problems related to the numerous structures that are necessary for the volumes to operate correctly. If problems are found, TechTool Deluxe can attempt to repair the damage to help reduce the chance of future problems. If TechTool Deluxe has discovered problems with the structure of a volume, allow the program to repair the problem. Quite often these issues are minor, but sometimes they can be indicative of a more serious problem. If the problem persists, consider backing up the device, reformatting the media, replacing the data, and then testing again.

I was also instructed to access the Apple site and download the most recent version of TechTool Deluxe that can perform repairs. I downloaded the software and followed the instructions to open the file in the Disk Utility app and burn a CD. Following the directions I then booted up on the CD by restarting the computer while holding the "C" key. The computer booted up on the CD and loaded TechTool Deluxe. I ran the same tests as above and once again the Volume Structure failed. When I clicked on repair it seemed as though the program was trying to fix the problem - then it abruptly stopped and stated that the Volume Structure could not be repaired.

I removed the TechTool CD, rebooted the computer, installed the TechTool Deluxe that I downloaded from Apple, and ran the Disk Utility. When I tried to "Verify" the disk this is what appeared: Disk Utility stopped verifying "Macintosh HD". This disk needs to be repaired. Start up your computer with another disk (such as your Mac OS X installation disc), and then use Disk Utility to repair this disk. Following these instructions I rebooted the computer using the Mac OS X installation disk - and the only option I found was for an installation of the OS.