Google -> many answers, but all missing a key bit of information. The group policy editing solution will change the registry. The registry change solution will change the registry. But there is nothing to prevent the registry key from being changed back by outside forces, such as Windows updates or domain level group policy.
I suggest that you follow your favorite registry hack, for example:
http://www.emailbattles.com/2006/01/11/vuln_aacgjahfig_ib/
then change the permissions on the registry key to a single known user, namely yourself. Remove inherited permissions using the copy current permissions option. Give full permission to your account, and delete all those other accounts.