My Computer occasionally reboots itself when I turn it off. Anyone know why it is doing this, please

The computer is new, purchased in April, and it has only just started doing this but not every time I click 'turn off computer'. It's almost like I clicked on 'restart'. Security on there is first rate and there have been no viruses, trojans, or worms on it, no spyware or adware. It functions perfectly and mostly when I shut down it doesn't restart. Anyone know what may be causing this? It seems to happen when I have removed cookies prior to shutting down. Thank you.

My Computer occasionally reboots itself when I turn it off. Anyone know why it is doing this, please?nortin

Shutdown problems in Windows XP are most commonly caused by what is know in computer circles as legacy hardware - old technology components and peripherals that are not Plug and Play (PnP) devices - and software-compatibility issues.

If your computer was shutting down, but all of a sudden it won't shut down properly, or it restarts during the shutdown, if you installed any new software or drivers, remove the software via Add/Remove Programs in the Control Panel, or use the Roll Back Driver feature in the Device Manager (right-click My Computer, click Properties, click the Hardware tab, and find the device, double-click on its entry and open its Driver tab) to restore the old driver. If you discover that a driver is the cause of the problem, try downloading and installing the latest driver for the device from its manufacturer's site. If you installed any new hardware immediately before the problem occurred, obtain the latest driver file available for it in the same way. If the device still causes the problem with the latest driver installed, try a different make and model.