HOW DO I OPEN A COMPACT MAC?  (2.1)
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       You need a Torx T-15 screwdriver, at least eight inches long, 
  available from any decent electronics supply shop, and a special 
  tool referred to as a "Mac Cracker."  (In a pinch you can use a 
  spring loaded paper clip or even a three-sided ruler.)   Before 
  starting clear off a large, flat work area and get an ash tray, 
  glass, or other container to hold the various small screws you need 
  to remove.

       First disconnect all cables, most especially the power cable.  
  For maximum safety you should only work on your Mac after it's been 
  turned off for an hour so that various high-voltage capacitors have 
  had time to fully discharge.  Lay the Mac face down on a soft towel 
  in your work space.  If you're working on a Plus or earlier Mac 
  remove the battery cover and battery.  Then unscrew all the screws 
  with the T-15 screwdriver.  There are four of them on SE's and 
  Classics, two hidden inside the handle and two above the ports on 
  the bottom of the Mac.  The Plus and earlier Macs have five screws 
  including one under the battery cover.  After the screws are 
  removed, wedge the cracking tool into the seam and pry the two 
  pieces of the case apart.  Then carefully lift the back cover off 
  and place it down in your work space.  Finally inside you'll find a 
  metallic RF shield covering the ports which can easily be removed.