This is where I got confused. The motherboard has 24-pin connector as you can see on the previous screens. The cable from the PSU has 20-pin and 4-pin but they're disconnected from each other. Does that mean I have to connect them together to make 24-pin and then connect it to the motherboard, correct?
Since you need a 24 pin you connect them together.
What are these cables for? Where do I have to plug them in? I have 2 separate cables like that coming out of PSU.
Those are the power plugs for the SATA drives such as the hard drive in your one picture. Take note of the key on the drive and cable and make sure they are lined up.
Idk what this cable is and where it goes. I have 2 of them.
That one the 6 +2 should have markings on them they look like they are the PCI-e for the video card.
This 8 pin is a 4 + 4 cable. It comes apart to make a 4 pin to go on the motherboard at the top to the rear of the CPU, The one you circle with a question mark. You need to look at them and decide which one matches the motherboard, they have square and circular on one side pins that you need to match up to the motherboard.
Cables that came with GTX460. Do I have to use them?
They are there to convert from the four pin power to PCI-e for the video card. Since you have two on the power supply they are not needed.
This is the back of the GTX460 SE v2.
Just to be safe make sure that plugs match when you plug them in. Notice that 3 pins are square and 3 have a arch on one side. Make sure the plugs match up just as a double check.
I find it hard to believe that the plugs have no markings, nor does the box have a illustration on it, or a sheet of paper showing what the plugs are for, however, it is what it is.
If it was my computer I would only hook up the two plugs to the motherboard and without the video card see if I got video on the monitor and then go from there.
Be careful not to mix up the 4 + 4 (CPU Power) and the 6 + 2 (2 of them)