IIRC you could actually run XP themes on 2k3 if you started the theme service. Under the hood they were almost the same exact same kernel (I think server / 5.2 had a slightly different IP stack and some server tweaks for task scheduling, shadow volumes and memory caching).
Likewise if you wanted the non XP (Luna I think it was called?) styles you could just stop the theme service and it was effectively win2k style.
Likewise if you wanted the non XP (Luna I think it was called?) styles you could just stop the theme service and it was effectively win2k style.