Common Methods of Opening Computers

Removing a side panel: 

This is the most common method, and usually requires the removal of one or two screws





Removing the entire casing: 

This is common in older computers, and requires the removal of between 3 and 6 screws.





Snap-off:

Some flat footprint desktop models have buttons on the side which, when pressed, release the case.  The small Gateway Essential computers of the last couple of years are opened in this manner.
 

 

Some unusual cases you may come up on include the following:

Pull out chassis: 

Some computers have a handle in the back, with which you pull the entire chassis out of the case.  Some older Compaq Presario's are opened in this manner.
 




Screwed in at the bottom of the computer: 

Some older Packard Bell computers actually have their side panels screwed in at the bottom of the computer.  You have to turn the machine upside down, unscrew the panel, and remove it from the computer.
 





Clamshell: 

Growing in popularity and very good.  The computer opens like a clamshell after pressing two buttons.