I just bough a new HDD some time ago and recently i bought another SATA cable to have both HDDs connected at the same time, to transfer all the files from the older one to the newer. When i connected both of them, the computer started working, i tapped F2 to go to bios to make sure it was detected, and then after 5-10 seconds the computer instantly shut down. After this incident, my computer won't start at all when connecting the SATA power supply to the old HDD. If i connect only my new drive, it works without any problem. If i connect only my old drive, or both the old drive and the new one, and then push on the power button, the cpu fan simply rotates about 5 degrees and then stops.. and that's it, the computer doesn't start, and no sound from the pc speaker either. Is there any way to recover my files from the old HDD and transfer them to my new one? I do not want to use the old HDD any more, i only need to save all my files.
Sounds like a dead hard drive. If you add a part to a computer and it stops working, then you remove the part and it works again, then it's pretty easy to deduce which part is giving you trouble. :)
Some things to try to make sure that the hard drive is completely dead and it's not some other issue:
1) Make sure you plugged in the appropriate cables to the hard drive. It sounds like you need 1 SATA cable and 1 SATA power cable.
2) As neomonks suggests, try switching the port you plug the SATA cable into on the motherboard.
3) Try a different SATA cable.
4) Try putting this hard drive into a different computer and see if you still get problems.
If you try all of those things and you can't get access to the hard drive, then it is dead as a doornail and you will need to send it to a professional hard drive data recovery place to access the data. These places can be expensive, so you might need to make a decision about how valuable this data is to you.
Please verify if the SATA cabe ordering is correct.
SATA cable on the motherboard starts from SATA 0,1,2,3.