A laptop computer is supplied with special-purpose software that detects when the cover is being closed by an unauthorized person. When the cover is closed, an alarm sounds using the speaker integral the laptop. The closed-cover condition is detected. The software operates on either interrupt-driven devices or polled devices which have some means for detecting that the cover is closed. The software includes a password feature and a hot-key feature for overriding the alarm so that an authorized person may close the cover without disturbing other persons or to stop the alarm if the authorized person forgets to disable the alarm.