I'm on a PC, and the sound balance is okay in every other program but Itunes. Yes, I've gone to the control panel>speakers etc etc.
edit: It's a Sempron 3000+ with a gig of ram. It's not the system that's not working. Old Itunes worked fine. The new one isn't putting sound out through the left speaker.
chances are, you're not gonna find help here. Have a look at a windows users forum, such as neowin.
With a PC, you can't pin a problem on one manufacturer, like you can with Apple. It may be your speakers which are at fault, or your sound card, or your motherboard, or a bug/virus in Windows...