As far as I remember the game is two CDs large, so at the very least your installation file (ie: whatever you downloaded) should be over 1GB. The installed game will naturally be much bigger.
Whatever the case though, this is now the third thread you've started trying to get help with your illegal version of the game. As difficult as it may be to get hold of a legal copy nowadays, this is not a place suitable for getting illegal versions to work properly
. LucasForums has legal agreements with LucasArts, and I'm not prepared to let that relationship be compromised by allowing you to get technical support with an illegal copy on this forum.
It's great that you've discovered Monkey Island and I hope you'll contribute to many great conversations about the game in the future, but the fact remains that if you start another thread seeking help with your illegal copy I'm going to have to ban you. Buy the game
or get help from whoever/wherever you got your copy from.