Sorry I don't know of any tutorials but to apply a theme you will also need to patch some system files, I have been using VistaGlazz
recently and it seems to work well.
If you download that theme you can get a 30 day trial of Restorator
to open the themes msstyle and you can then extract the image folder and go through them untill you find the one that looks like the start menu with COD on it and then you just need to edit that image and put your own on there and then add that back to the msstyle using Restorator again.
You will need to purchase Windows Style Builder
if you want to create your own themes and you can get Photoshop CS4 Extented
on a 30 Day trial if you don't have any decent editing software.