Theme change to classic when I boot computer

Hello,
I have Windows Vista Ultimate (32 bit) intalled on my computer. Everytime I boot my computer it changes the theme to windows classic theme. I change it back to the windows vista theme. Switch it off and back on and we back where we started... windows classic.

I even deleted the classic theme to stop it fromdoing that, but the same thing keeps happening.
I've tried everything. I dont know what's causing it in the first place. but dont know what to do anymore.
Please help.