This might help One button shutdown for xp, control panel, power options, advanced tab, in the middle it say's power buttons, in drop down tab click shutdown. Then click apply and ok. Then on your computer, on- off button, push it and your computer will shut down. one step shut down.
Make sure APM (Advanced Power Management) is enabled in your bios.
Do you have a Geforce card? If so disable desktop manager by right clicking the tray icon and selecting nView desktop manager-check 'disable nView'.