Install the three things here (
http://www.lucasforums.com/showthread.php?s=&threadid=79875)
Vdmsound mode:
Click setup
Select Monkey Island 1
Click Browse
Select the folder where the monkey.000 and monkey.001 files are.
Select Monkey Island 1 on the main screen, click start.
ScummVM mode:
Select Monkey Island 1 from the list
Click Browse
Select the folder where the monkey.000 and monkey.001 files are.
Sound mode - select adlib
Graphics filter - whatever you want
Tick - write scummvm.ini if you want to save the settings
Click run