autorun.inf

Autorun.inf is a file that Windows checks when a CD is inserted.  It looks like this:

[autorun]

OPEN=cdrun.exe

 

When Windows finds an autorun.inf file on a CD, it will look for the OPEN= line and launch any program it finds referenced there.  Autorun.inf has to be located in the top-level folder of a CD to work (not a in a subfolder).