Learn standard startup key combinations used for troubleshooting most Macintosh computers in Mac OS 8 and 9. Some functions may not be applicable for every Macintosh computer.
Reset the PRAM
Hold down the Command+Option+P+R keys during the restart sequence. The computer will beep for a normal startup and will beep again. When you hear the second beep, release the keys.
Turn Off Extensions
Hold down the Shift key at startup until you see the Welcome to Macintosh screen.
Rebuild the Desktop
Start or restart the computer while holding down the Command-Option keys.
Disable Virtual Memory
Hold down the Command key at startup. Do not release the key until startup is complete.
Extension Manager
Bring up the Extension Manager at startup by holding down the Space Bar.
Force Reboot
Force reboot by holding the Command + Control + Power key.
Startup From Bootable CD-ROM
Hold down the letter c key upon boot (lower-case only).
Eject floppy or other removable media
Hold down the mouse button on boot.