One thing you can do is make your background image one logo (one little section of the large image you are currently displaying) and have it repeat. As it is now, the image creates a vertical and horizontal scroll bar, and it centers and leaves white space on all sizes in a larger window.
Like Stiney said, people with 800 x 600 monitors are pretty used to scrolling as they are now the minority. I'm one of those dinosaurs that still uses tables because CSS code displays differently from browser to browser (sometimes radically), and I set them to percents to accommodate any size browser window.
I agree as well that songs should be selected to play, not automatic. There are a lot of cool mp3 players that you can use.
XSPF Web Music Player (Flash) - Plays MP3 on your website
FREE Flash MP3 Player
embedded Free MP3 Flash Player for myspace, blog and your web sites