What do you need to install in your computer so you can put your own DVD movies into it and watch them?

What you need is a DVD drive. Today they are rather cheap. www.pricewatch.com is a great source for checking out prices. There are also DVD writable drives where they can create dvds, but they are more expensive. All you do is buy a DVD drive that works with your computer (call the manufacturer or check manuals to be sure), install it yourself using the manual or ask/pay someone else to do it. Install any software it requires and you can then watch DVDs on your computer.