ViStart not only offers the Vista style eye-candy and transparency for XP, but also the highly regarded quick search function of Vista. ViStart was designed to be included in the Vista Transformation Pack, however you can grab a stand alone version if you would prefer not to install the entire pack. ViStart is lightweight, skinable, and another great feature of Windows Vista brought to XP. ViStart is a free download for Windows XP only.
ViStart
More...