it may be an old tip but...
Like previous versions of windows, it takes long time to restart or shutdown windows xp
when the "Exit Windows" sound is enabled. to solve this problem you must disable
this useless sound.
click start button then go to settings -> control panel -> Sound,
Speech and Audio devices -> Sounds and Audio Devices -> Sounds,
then under program events and windows menu click on "Exit Windows" sub-menu and highlight it.
now from sounds you can select,choose "none" and then click apply and ok.
now you can see some improvements when shutting down your system.