Software to make themes/Logons for Windows

Hi,

I'm really impatient for start to make my own themes, but I couldn't find any software than can make files .theme or .msstyles.

I've been working with "Stardot's Skinstudio Professional", but this soft doesn't export a .theme or .msstyle fiel.

Any suggestion?? Id like to customize my themes or boot screen image

Thanks!