When doing star power pull the guitar up like you would when using star power and it will highlight yellow on the screen, you can also use the select button on your guitar if you don't wanna use the pull up function while playing

It works great in my box (which has a geforce 8800 GTS G92) with updated drivers and Vista 64bits, I even got a second guitar to play co-op (the xbox guitar, it's the same that comes with this bundle), custom songs can be also added using "guitar hero three control panel" after applying the 1.3 patch for the game.