How do you add a new hard drive to a computer?

It really depends if it is internal or external, with an external, you just plug it in via usb (if you're running XP), but if you have an older version of Windows, you might have to install drivers for a external. With an internal drive, you should just be able to open up tha computer, connect the IDE cables, then you should be ok. Go to the following site for help with an internal drive: