Command-command-~ is supposed to bring up a monitor through a non-maskable interrupt, into which you can enter the command ? for info on available commands. "halt" saves files to disk and gracefully halts the system. "mon" goes to the ROM monitor but does not gracefully halt the system. An emergency shutdown is available by pressing <left alternate>-<left command>-<numeric keypad *>. (on an ADB keyboard, use the command bar instead of the left command key). This will not power off the computer but will do a hard reset of the CPU. This does *not* result in a clean shutdown, and can damage an optical disk if it's in the middle of a write operation (so I hope you didn't just do it ;-) ). - Mark