If the user can change theme they can also remove the eyacandy.. its very easy. Just right click and personalize. You got all there.

Well not all security is gone if you turn of the user stuff. You still got the same base security.
I can run XP on a old laptop, but not any Linux on it.. it damand to much..
Even with Linux if you want fancy stuff it demand much.
Well some stuff need to be rewritten, but thats for most part porly written from the start.
WGA is easy to get past. it just take a program to do it.. There also other trick you can use. You can update and so on without any problem also. MS knows this to well already.
well I cant use Linux so much.. I play games and program windows stuff. :-9
Greetz