Click Start, right click My Computer,
click properties,
click advanced tab,
Under Performance, click Settings button,
Scroll down and click to add a check mark in front of - "Use drop shadows
for Icon Labels on the desktop."
Apply and Ok back to the desktop.
You may have to reboot to take effect.
Desktop icons and icon labels may not display background transparency or the
drop shadow effect in Windows Server 2003 and Windows XP: http://support.microsoft.com/?kbid=305117