My iMac g3 was working fine. I went into the startup disk options, and chose os 9 to be my startup disk, and then I restarted. Now, it shows a floppy disk and a question mark. What keys should I hold down on boot up to get a boot menu, so I can get into OS X and change my startup disk? It doesn't have to be a bootloader, just a way to get into OS X to fix it...