Uxtheme Multi-patcher will allow you to use any 3rd party msstyle theme on Windows XP/SP1/SP2 or Windows Server 2003 (with Themes enabled) just by patching the uxtheme.dll (dynamic link library).
What’s New in version 8.0:
Added Windows 7 Service Pack 1 compatibilities check
Removed software incompatibilities restriction check since memory-patching is still safe in this case so user can use it in any platform regardless of being beta or newer
Updated patching engine to Rafael’s latest UXStyle.com