First Aid failed - now what?

As it clearly states in the Disk Utility/First Aid window, you cannot repair your hard disk from the same start-up disk. Reboot from your install disk (holding down the C key). Once it opens, select your language, and then go to Disk Utility from the Utilities menu. Select your hard disk as before and click Repair.

Once that is complete reboot again from your usual start-up disk.

I had no intention of giving you that impression and nor do I think that. If my wording made you think that I apologize.

The hard disk inside your Mac is your start-up disk, the one you start your Mac from. It cannot repair itself, so you need instead to start up from the install disk that came with your Mac - this why it is so important to have it.

Place that DVD in your superdrive and go to the Apple menu and click on Restart. Hold down the c key on your keyboard until your Mac has started up. This will take a bit longer than when you start from your hard disk.

You are NOT going to install anything, but just select English as your language (assuming that it is!), and ignore the next (install) window that appears. Go to Utilities in the menu at the top of the screen, and go to Disk Utility. Select your Hard Disk and click on repair.

This will take a little while and you will see all kinds of messages in the window, all of which you can ignore. Finally it will say Disk Repaired, and you then restart again without holding down the c key, in order to start up again from your built-in hard disk.

You're welcome!