Dell Vostro 400 Owner's Manual page 17

13 power button,
power light
14 drive activity light
Press the power button to turn on the computer.
The light in the center of this button indicates
power state. See "Controls and Lights" on page 172
for more information.
NOTICE:
To avoid losing data, do not use the
power button to turn off the computer. Instead,
perform an operating system shutdown.
The drive activity light is on when the computer
reads data from or writes data to the hard drive.
The light might also be on when a device such as a
CD player is operating.
Setting Up and Using Your Computer
17