My desktop Theme won't change!??!?

For some reason when i put my theme to the xp look or anything else it stays to the classic look. Any cure for this?

What is the extension of the theme?
Is it program specific? (Only runs on Window Blinds, Style XP, etc.)
What are you using to display the theme? Window Blind, Style XP, Win XP?
Where is the theme located on your PC?
Are you using Windows or Mac?

Simply stating that the theme doesn't work, does not allow us to help you.

do you have themes disabled?