Flashing ? folder can't find HD

I have tried to repair the disk using disk utility but I am getting Filesystem verify or repair failed message. When trying to reinstall OS X, my hard drive never shows up. I cannot boot in safe mode. Any help would be appreciated.

This all happened after I came back from a week vacation. I shut the computer down before I left and when I came back, I got the flashing folder with the ? mark in it.

HD failed, now what?

Ok, if the HD has failed, and it seems it has...now what? Any way to recover the data? No funny sounds coming from computer. When I use disk utility, I can see the HD and the main Drive smart status says verified. But when I select my HD (it is greyed out) it gives me capacity but not any used or available information. Is it toast? Can I get anything back? I have backed up most photos, music and files on external but not yesterday. There is some stuff I would like to get since last backup. Any help very much appreciated.

I was able to get the installation process started. From there I went into disk utility and tried to repair my "macintosh HD" (which was greyed out.) Error: Filesystem verify or repair failed. This is the message I get. When I try to reinstall OS from the dvd, no, my disk does not show up.

In disk utility from the OS install disk, it shows my WD2500JS-40TGB0 Media drive and in the infomation at the bottom, it says the S.M.A.R.T. status: Verified. When I click on the "Macintosh HD" which is located under the WD2500, it is greyed out but it lets me select it, shows a capacity of 232.6GB but does not show available or used or number of files information.

I am considering purchasing diskwarrior but want to make sure it can help my situation before I purchase it. My imac will not boot from the internal hard drive (Intel processor) When I use disk utility to try and repair the disk, I get error messages and it won't repair. When I connect using target mode with my mac book pro, the hard drive does not appear on my host (macbook pro) computer. I have reloaded OS X (Leopard) (but original was OS X Tiger 10.4.something) onto a firewire external drive and can boot my imac that way but I can not find my original internal Macintosh HD. Will disk warrior be able to help with this scenario. I would really like to access that internal Macintosh HD and retrieve my files. Thank you for your time.

Got a demo version of Data Rescue 3 and it could not read the data during quick scan or deep scan and I now have it trying to clone the drive to my external HD. It says it is going to take 5 days (118 hours). Is this even worth trying? Can the good folks and my local Apple Store Genius bar help? I am going to take it in and see what they say but if anyone has any advice I would appreciate it.