The laptop case can be made out of assorted materials, plastic is the most common.
A notebook isn't like a normal computer case, opening one can be an adventure. Having worked on Compaq, Dell, HP, and IBM laptops all the cases are opened differently and are all difficult to crack.
Disassembly of a laptop case or to take apart a notebook "shell" unfortunately is a time consuming process, and you must exercise caution when opening the it or you may have to replace the broken parts of the case. Most have screws located under the battery, keyboard, and in the hard drive bay. In addition if you have to remove the video screen you will have to be extremely careful to not tear the ribbon cable for the screen.
The notebooks I am most familiar with are the IBM ThinkPad series. Some of these procedures apply to other laptops.
You will need a lot of open space and a container for small screws and parts.
A magnet or magnetic screw driver is useful for getting the small screws out of recess or wells that the screws drop into. Another tool that is very useful is a thin plastic putty knife (I will tell you why shortly).
If you have an exacto knife you can use it to remove the little covers over some of the screws, these little plastic covers are coated with an adhesive on the back to keep them in place, I put them on a piece of paper with just enough force to keep them from falling off. This will keep the adhesive intact for replacing them when you put you computer back together.
Once you have all the screws out of the notebook case, take your plastic putty knife and find a spot where you can insert it in between the bottom and top halves of the notebook case, gently work it along to 'crack' the case apart. To keep it from closing you can put a flat head screw drivers (or more plastic putty knives) in strategic points to keep the case from closing back up.
Now that you have it open you can proceed with your repair/replacement.
02/13/14 - When I wrote this article in 2008 ASUS had just begin making their own laptops. Most of the ASUS laptops have a panel on the underside of the notebook that slides off, however the challenge comes with all the screws in some laptops, I currently have two laptops and a netbook that I have done upgrades for. Once you have taken all the screws out of the panel it will side off giving you access to the memory, processor, hard drive, and with the ASUS K50IJ Notebook Upgrade notebook you have access to the motherboard as well with out removing any thing else.
can get a