Apple MacBook Pro 17-inch (original, Core 2 Duo, 2.4GHz, Late 2007 CTO, Early 2008, and Late 2008) - Manual (Page 160)

MacBook Pro 17-inch (original, Core 2 Duo, 2.4/2.6GHz, 2008) Troubleshooting — General Information 160
Resetting the System Management Controller (SMC)
Power management is now handled by a chip called SMC (System Management Controller).
Previously, it was handled by the Power Management Unit (PMU). To reset the SMC:
If the computer is on, turn it off. 1.
Disconnect the power adapter and remove the main battery. 2.
Hold the power button down for five seconds, then release. 3.
Install the main battery and connect the power adapter. 4.
Press the power button to restart the computer. 5.
Display off and sleep indicator light on
When the system is running but the video is not illuminated (for example, briefly upon startup,
or when energy saver dims the video while the system is still awake), the sleep indicator light
remains on. This feedback is to alert the user that the system is not shut down. It is possible,
however, that this signal may fail if the system has crashed. As such, you can use the next test to
see if power is present in an apparently “off” system.
System powered test using Caps Lock LED
There are situations when the system is giving indications that it is shut down (no sleep light, no
hard drive access, screen is dark, no fan, and so on); however, the logic board may still be active.
In this case, the logic board is drawing power and generating heat.
Warning: In this situation, if the computer is placed in an enclosed environment like a
carrying bag, the computer can overheat.
You can potentially verify this situation by pressing the Caps Lock key. If the LED glows, the
power manager is actively running on the logic board. If pressing the Caps Lock key or other
attempts to wake the machine have failed (including closing the lid to put it to sleep and
reopening it to wake it), hold the power button down for six seconds to force a shutdown of the
computer. Restart the system to check that it starts up normally.
Note: Given that the keyboard in MacBook Pro is a USB device, it may not respond if the
operating system has crashed. Thus, despite the fact that the caps lock LED does not light up, the
computer may still be drawing power. If in doubt, hold the power button down for six seconds to
force a shutdown of the computer.