The clue here is your install of XP. What many expected is that Microsoft would install drivers for motherboard, BIOS and more.
Nothing is farther from reality. "Current" drivers are handled by the person who installs the OS, not by Microsoft, Windows Update or that demo-button "driver update."
Since doing a full reinstallation of XP a few weeks ago I have had to sort out several problems (especially with the deleted registration keys of various programs) but one problem still remains. When I go to TURN OFF COMPUTER I get to the window with the three buttons and TURN OFF and RESTART are fine. The left button, STANDBY, however, is greyed out and will not work. I have also done a limited reinstallation but that has not fixed the problem either. Grateful for any help here.