This is an unreleased and unsupported theme developed by Microsoft before reaching a final state with the "Royale" theme, which ships with Media Center Edition. This theme does not require a custom UxTheme.dll file.
If you have the Royale theme from MCE installed, you will need to remove it before installing this one (both use the same name).
If you have the Royale theme from MCE installed, you will need to remove it before installing this one (both use the same name).