Add new Themes to XP
To add new themes to XP:
1) Download Neowin UXTheme Multi-Patcher v4.0 to patch your UXTheme.dll file. (Don't worry the program can reverse the process)
2) Download new themes. (My personal favorite is Milk Vista)
3) Extract the files and place then in your C:\WINDOWS\Resources\Themes folder.
4) Change the theme like normal.