One way to access the Mac's boot menu
Do you use multiple partitions on your Mac? Maybe you use Apple’s Boot Camp tool to boot your Mac into Windows occasionally, or maybe you’ve got a Mac Pro loaded with four drives partitioned into 16 different virtual drives. Whatever the reason, if you’ve got a bootable system installed on more than one drive or partition in your Mac, you’re probably familiar with the boot manager—this is the screen that shows the bootable drives on startup (or reboot).
You can make this screen appear by holding down the Option key during startup, which is the typically-prescribed method. However, if your machine seems to be ignoring the keyboard at boot time (which is a problem I’ve heard about, but not experienced myself), try this tip, courtesy of Mac OS X Hints reader GanjaManja.
If you’ve got an Apple Remote for your Mac, you can use it to activate the boot menu. Just hold down the Menu button on the remote as the Mac boots up. (If your Mac doesn’t recognize your remote, check the Security System Preferences panel to make sure it’s set to accept commands from the remote. You might also want to pair the remote with your Mac, so the Mac only responds to that particular remote.)
I tested this with my MacBook Pro, which has three bootable systems on it (the ExpressCard SSD, the internal 10.6 drive, and the Boot Camp Windows partition), and it worked as described.