Although Microsoft Defragmenter (Defrag) sorts directories and files,
no detectable system activity occurs while Defrag is running. The Power
and Advanced Power Management (APM) utilities may assume the system is
idle and therefore suspend the system. Pressing the ESC key causes an
interrupt, making the system resume its activities.
Defrag does not query for currently active Power or APM services. If
the system goes into an idle state while Defrag is running, you should
press the ESC key. Do NOT reboot or turn the machine off; doing so can
lead to data corruption.
To prevent Power from interrupting Defrag, disable Power and APM
services before running Defrag. Microsoft recommends that you run your
laptop computer from an AC outlet when you run Defrag.