For several years now I have put up with XP Pro not shutting down at power off but rebooting, I have had to hold my finger ready to press the button. Now all is as it should be and the only thing I have done recently is to remove a redundant Dial up Modem PCI card, no drivers etc were installed as when I went to BB and did a reinstall I never bothered to put them on. I only left it in to fill the hole in the case. So that must have been the cause even whilst in use. I only post this as it may help others who have the same problem as I did, the cause may be the same, who knows. The mind boggles at times.