Stumbled accross this bit of info while browsing, apparently it`s not enabled by default but could help improve OS security.
Some info about it ->
http://support.microsoft.com/?scid=k...y=13#appliesto
Please do not do this if you don`t have a good back up solution or are unfamiliar with the registry, do at your own risk
p.s. No probs here and it is from Microsoft!