today my 27" iMac i bought a year and a half ago suddenly because really sluggish. i checked the processes to see what was causing the problem. nothing seemed to be taking up large amounts of resources so i rebooted. again, sluggish so i rebooted again. soon thereafter i decided i should try and repair disk permissions so i fired up Disk Utility and saw the HD listed in red! "S.M.A.R.T. Status: Failing" and something about taking the computer in for repairs as soon as possible. before i lug this beast downtown to the Apple Store, i decided to do a bit of testing, research, but nothing i found on google seemed to exemplify what i was experiencing. sure, there are lots of posts about failing S.M.A.R.T. drives, but there is more: now the computer doesn't boot up. i get the white background with gray apple logo and the spinning gear, but it will spin forever and not actually boot. i can't bootup with any DVD. i've tried the install DVD that came with the computer as well as a TechTool Pro boot DVD. while pressing "C" should boot the computer from the DVD drive, the DVDs try loading and then simply eject. more, pressing "option" to choose which drive to boot from only returns one option: "Macintosh HD". i've unsuccessfully tried to boot in Safe Mode by pressing "Shift". in doing so, the gray apple logo appears and the spinning gear. minutes later the machine will restart, only this time i will see a blinking folder icon with a question mark. additionally, i've unsuccessfully tried to boot in Single-User Mode by pressing "Command + S" as well as Verbose-Mode by pressing "Command + V". both modes display command line prompt while booting up, but it eventually hangs and i'm never able to execute any commands. Single-User mode makes it to: while Verbose Mode stalls at: Finally, i've reseated the RAM with no luck and the Apple Hardware Test was run by starting my machine and holding "D". i've run both a regular (~10 minutes) and extended (~1 hour) testing with AHT. both tests return no hardware issues found. (??!!) does anyone have any insight on this? if it's simply the HD that has failed, then why am i not able to boot up using a DVD and why hasn't AHT found any problems with the hardware? could it be the logic board? power supply? bad RAM? if so, again, shouldn't the Apple Hardware Test spotted these issues instead of passing everything with flying colors?