1: Research your machine
Before we start the process of adding a drive, we need to do a small amount of research inside your machine. The goal of the research is to find out if it will be easy or not so easy to add the new hard drive. We also need to find out what kind of drive you need to buy. You may be able to do this research by reading through your computer's manuals, but it is far easier to simply open the case and look inside.
The first question to answer is: How many hard disk drives have already been installed inside the case? In the majority of machines, the answer to this question is "one." Having only one hard disk drive installed makes it easy to install another one. After you open up your computer's case and look inside, you will probably find one optical drive (a CD or DVD drive), a single hard disk drive and perhaps a floppy disk drive. The optical and floppy drives will be easy to find because you can see them on the outside of the case. The hard drive may take a little searching. If you have no idea what a hard drive looks like, look at the photo above.
If there are already two drives installed inside your case, then adding a new one is more difficult.