Connect the other hard drive to the same data cable and power it from the SMPS. Before connecting, ensure that the second drive, which you are going to connect is set as slave. This can be done by changing the jumper setting of the second hard drive. Which jumper is to put or remove is usually mentioned on the hard disk itself.
Now boot on the machine. The secondary drive will come as extra partitions when you open my computer. Now you can copy your files.
Switched Mode Power Supply. If you are using a desktop, it will usually be at the top-back corner of the cabinet. This is the power distributor to the different units of your PC. In your PC you will have two wire conections to your hard disk, one is the data cable, coming from the mother board, the other (usually in four colours, red, white, yellow, black) coming from the SMPS.
You can see it if you open the cabinet..........