iMac presents symptomatology of HDD failure & Graphics Card failure!

"I only read the first half of your question because I think I know the possible problem after the first two sentences.

This should be your machine:

Apple iMac ""Core 2 Duo"" 3.06 24-Inch (Early 2009) Specs

Identifiers: Early 2009 - MB420LL/A - iMac9,1 - A1225 - 2267

Apple was just switching over to the proprietary Apple hard drives at this time that require specific Temperature sensor cables for each brand of hard drive. At least they did with the late 2009 machines. This may not be the problem at all but I think it's worth a shot for $8.50: http://cgi.ebay.com/IMAC-HARD-DRIVE-TEMP...

922-9223 Hitachi

922-9224 Seagate

922-9225 Western Digital"

"From yesterday i run again the system with no problem. Today i decided run again the hardware tests to see if the errors are again there.

The EFI hardware test showed no errors. After the completion of the test, there was a very strong ghost image of the Hardware Test window...

:(

The Apple hardware test (command + D on startup) returned the following error:

4M0T/1/40000003: HDD - 1420.

Same errors found here: https://discussions.apple.com/thread/184..., some of them presenting the same symptomatology as my iMac. One of the guys managed to solved the problem through apple service which replaced the fan, and heat sensor. But which one?

Moreover i boot mac os x on terminal mode (command + S) and i typed:

/sbin/fsck -fy

and the result was: the volume appears to be OK (? confict results eh?)"