Samsung NM40 User Manual page 20

If the computer does not turn off properly due to a system error, press
<Ctrl>+<Alt>+<Delete>. When [Windows Task Manager] dialog box appears,
click Shut Down > Turn Off to turn off the computer. Your unsaved work may
be lost/damaged.
If <Ctrl>+<Alt>+<Delete> keys do not operate either, press the power button
for more than 4 seconds to turn off the computer. Your unsaved work may be
lost/damaged. When you turn on the computer next time, it will perform a disk
checking process.
Getting Started 7