IMac shuts down on 1/3 of boot sequence

Hello,
My 20 inch 2007 iMac suddenly started shutting down on 1/3 of boot sequence. This happened after the mac just shut down while i was working on it, since this happened the mac will not boot. The Apple logo appears, the loading bar appears, it gets to 1/3 off the bar, then it disappears, and the mac shuts down. I already used the disk utility to check the disk, there seems to be no problem. Also, i already re-installed MacOS, this did not have any effect as well.
Does anyone know how to fix this problem?
Mac info:
iMac 7,1 20 inch
Processor: Intel core 2 duo, 2.4 ghz
4GB of Ram.

Reinstalling OS X Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Reinstalling OS X Without Erasing the Drive
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list. Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu.
Reinstall OS X: Select Reinstall OS X and click on the Continue button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
Also see:
Reinstall OS X Without Erasing the Drive
Choose the version you have installed now:
OS X Yosemite- Reinstall OS X
OS X Mavericks- Reinstall OS X
OS X Mountain Lion- Reinstall OS X
OS X Lion- Reinstall Mac OS X
Note: You will need an active Internet connection. I suggest using Ethernet
if possible because it is three times faster than wireless.

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