A patched uxtheme.dll gave you the freedom to use un-signed custom visual style in Windows XP but in Windows Vista you have to replace three dll files to use third party visual styles.
Those three files are uxtheme.dll, shsvcs.dll and themeui.dll
Download The Corresponding Patched Files: Within Windows
How To Install
1. Login as a user with Administrative privileges -or- have Administrative credentials ready (check under the keyboard for a slip of paper).
2. Navigate to %systemroot%\System32
3. Right-click uxtheme.dll and click properties.
4. Take ownership of the file and close dialogs.
5. Repeat steps 3 and 4 for themeui.dll and shsvcs.dll
6. Right-click uxtheme.dll and click properties.
7. Give yourself (or group) Full Control permissions and close dialogs.
8. Repeat steps 6 and 7 for themeui.dll and shsvcs.dll.
9. Rename uxtheme.dll to uxtheme.old.
10. Rename themeui.dll to themeui.old.
11. Rename shsvcs.dll to shsvcs.old.
12. Copy patched files into %systemroot%\System32
13. Reboot (yes, this is really required)
Now click HERE
and download any custom visual styles you care to use!
Attached is my desktop after patching the mentioned system files and downloading a custom visual style.