How does a touch screen work?

The touchscreen is used as an input device that can replace the keyboard and/or the mouse.

More about the technology behind the touch screens you can read here

What is DVD Dual layer?

Using Dual Layer recording DVD-R and DVD+R discs can store more data, up to 8.5 Gigabytes per disc, compared with 4.7 Gigabytes for single-layer discs. Many new DVD recorders support dual-layer technology.

How can I disable the shutdown button on my keyboard?

If you run Windows XP you can try the following:
Start -> Control Panel -> Power Options -> Advanced -> When I press the power button on my computer -> choose “Do nothing” from the drop-down menu.