Go: You can use the following startup key combinations on intel-based MAC computers
Hold down the C key at startup-Boot from a bootable CD or DVD disc, such as a randomly shipped MAC OS X installation disc.
Hold down the D key at startup--if you insert install DVD 1, start with Apple hardware Test (AHT).
Hold down the OPTION-COMMAND-P-R key until you hear two beeps-reset NVRAM
Option key at startup-start into startup Manager, you can choose to boot from a Mac OS X volume. Note: Hold down the N key to display the first bootable network volume.
Hold down the Eject, F12 key, or hold down the mouse button (/trackpad)--eject all removable media, such as a disc.
Hold down the N key at startup-try to start from a compatible network server (NetBoot).
Hold down the T key on startup-start as FireWire target disk mode.
Hold down the Shift key at startup-start in Safe mode and temporarily close the login entry.
Press and hold the COMMAND-V key on startup-start as Verbose mode.
Press and hold the Command-s key on startup-start as Single-user mode.
Press and hold the Option-n key at startup-starts from the NetBoot server using the default boot mirror.