this thread for vista themes which can be installed on winxp, and please dont forget to mention the site from where u hav downloaded and if possible also give a small screenshots of the theme.... u can also share ur own created vista themes.... 
vista themes for WinXp
vistastyles.org
you need style xp
you need style xp
......or windowblinds,if u prefer transparencies.
try vista anthracite pack