Dear me of 2005: Start learning how to play the guitar, there is nothing wrong with being an introvert, you don't need a girlfriend, and DON'T SELL THE PLAYSTATION 2.
Dear me of 2009: Take the music/audio production courses now. Otherwise you'll spend the next few years barely getting through classes, completely miserable and apathetic because you have no idea what you want to do with your life. Also, save up your money. Seriously, if you realized how much money you put in that vending machine throughout one semester alone, your jaw would drop. You'll need that money later for some expensive music equipment and software. Also, start learning Japanese. Just trust me on this.