Dell OptiPlex G1 - Manual (Page 6)

Power button Turns computer on and off.
Power indicator Lights up when the computer is on.
Reset button Initiates a hardware reset. To avoid possible data or file structure corruption, use
the reset button only when the system cannot be rebooted with the
key combination, and close any open application programs
or files if possible.
Hard-disk drive access indicator Lights up when the hard-disk drive is being accessed.
Diskette-drive access indicator Lights up when the diskette drive is being accessed.