My laptop shuts down during scans with programs such as Norton Antivirus or Spybot Search & Destroy. Does this indicate there is something nasty on the computer which does not like being scanned? The computer is running Windows XP Home Edition.

A likely explanation of this behaviour is that the laptop power management is launching after a period of inactivity. Many computers (in particular, laptops) have advanced power management features allowing the machine to go into low-power modes (e.g. standby or hibernation) after a particular period of inactivity. These low-power modes are designed to help conserve power and are especially useful for laptop computers running on batteries. However, many of these power management features are still set to trigger even when laptops are running on mains power. Because the scans conducted using Norton Antivirus and other utilities (such as Spybot) take a long time to complete, the computer is possibly going into one of these low-power modes due to the period of inactivity (i.e. no user interaction) during the scanning process.

For laptops on mains power, the hard drive is generally set to turn off after 20 minutes of inactivity and the computer will go into standby after 25 minutes of inactivity. I imagine the average full virus scan and/or spyware scan exceeds these timeouts, and therefore the computer may be going into a low-power mode which gives the impression the computer has shutdown. To check these values on your laptop, go to the ‘Start’ menu > ‘Control Panel’. Open the ‘Power Options’ control panel (you may need to click the ‘Performance and Maintenance’ category first). Click the ‘Power Schemes’ tab and look at the timeout values for the various power saving options. Should you wish to change the settings, you can either modify the settings in the current ‘power scheme’ (most likely ‘Portable/Laptop’), or you can select and enable another power scheme using the drop-down box (e.g. ‘Always On’) which will never put the computer into standby when on mains power, but instead will only put the monitor into standby mode. Just be aware, putting the computer into a more power hungry mode may cause the battery to be drained quicker when running on battery power.

Where the power management settings are not causing the problem, the screen saver may be conflicting with the scan. Screen savers are basically programs which have been renamed with the .SCR extension so Windows recognises the file has a screen saver file. There is a possibility the screen saver may be conflicting with one of the scan processes (e.g. since the scans are quite processor intensive, the added load of the screen saver may be causing the computer to crash and shutdown). If you have a screen saver enabled, try to disable the screen saver (through the ‘Display’ control panel > ‘Screen Saver’ tab) to check whether this solves the problem.

If disabling the screen saver does not solve the issue, we need to check whether some other process is starting after a period of activity, causing a conflict with the scan. To test this theory, run a scan using Norton Antivirus or Spybot while sitting in front of the computer. Make sure you move the mouse every 5 minutes to simulate activity on the computer. Should the problem not occur, then the problem may be related to some process starting after a period of inactivity. In this case, try closing all processes running in the background prior to running the scan, to narrow down the issue to a particular process. Press CTRL-ALT-DEL to open the Task Manager. In the window that appears, click the ‘Processes’ tab. Click the ‘User Name’ column to sort the names by user name (if this column in not visible, enable the column through the ‘View’ menu > ‘Select columns’). Close all non-essential processes running under YOUR user name (do not close processes running under any other user name). Try running the scan. If the scan runs to completion successfully, restart the computer and close all but one process. Run another scan. Should the scan be successful, restart then close all but two processes. Repeat this procedure until the problem occurs again. This process of elimination will allow you to track down which process is causing the problem.

However, if the problem is not caused by some process starting after a period of inactivity, there is the possibility some nasty malware or virus has installed on your computer, causing the computer to shutdown during the scan when the nasty is detected by the scanner. Try booting the computer into Safe Mode and running a scan using Norton Antivirus, followed by Spybot. Safe Mode is a special diagnostic mode of Windows which does not load any non-essential drivers or processes. Hopefully, this will prevent the process causing the problem from loading. To boot into Safe Mode, after the POST (but before the Windows splash screen appears) starting tapping the F8 key. The Windows boot menu should appear, from which you select ‘Safe Mode’. Once you are finished in Safe Mode, simply restart Windows to boot back into Normal mode.