WindowsX has made us a patch that will change your uxtheme.dll on Windows XP (Gold) SP1 and Windows Server 2003. You can also restore the original file with this patch.
I will be adding this to the header of the Customizing Windows XP forum too. When SP2 for Windows XP is released we will have an updated version posted as soon as possible.
WindowsX is currently working on projects such as Longhorn Sidebar for Windows and a very complete Longhorn transformation pack for Windows XP exclusively on Neowin which is being hosted by generous Neowin members and Tech-Critic