QUESTION:
 What happens to the aluminum in a optical disk when a high powered laser 
 stores information on it? 
ANSWER: From Tom Comeau April 15, 1996:
The aluminum stays trapped in the plastic, it just moves around a bit.

I know my journal made it sound like a big death ray was blowing holes in the
disk, but in fact the power involved is pretty low.  The aluminum sheet 
between the plastic is very thin, so when you heat it (for example, with 
a laser) it just melts back away from the heated spot, leaving a little 
pit in that spot.