Since going back to standard XP Pro I thought is there a way of making it look a bit more modern. I didn't fancy messing round with the theming DLLs and using what essentially amount to substandard themes.
I thought how about getting the MCE2005 UI on Windows XP Pro (not a recreation of it but the actual one). A few minutes Googling gave me my answer, Microsoft New Zealand had accidentally released the Royale theme, unfortunately they pulled it soon after. Luckily this being the Internet the cat can never go back in the bag.
The MCE2005 Royale theme for Windows XP is available at the link. You just need to run the installer and it puts it in the right place.
For those that like things a bit darker there is a Royale Noir theme leaked from Microsoft that did not make the cut into MCE2005. You can download the files here. You need to install this after the Royale theme. Extract it to c:\WINDOWS\Resource\Luna Noir. Then double-click on the luna.msstyles file, this will then give another sub-option to Royale on the Appearance tab in display settings.