By default, Windows XP turns on a lot of shadows, fades, slides etc to menu items.
Most simply slow down their display.
To turn these off selectively:
Right click on the My Computer icon
Select Properties
Click on the Advanced tab
Under Performance, click on the Settings button
To turn them all of, select Adjust for best performance
My preference is to leave them all off except for Show shadows under mouse pointer and Show window contents while dragging