Group Policies in Windows 2000 Server

I have a Windows 2000 Server with clients having Windows XP Professional. I have applied group policies in active directory but few of them are not applying on clients like i have disabled “Run Menu” in start menu in policies while it is not hiding on clients (Win XP Professional). Is it due to Windows XP? or any other reason. I know a trick that i can hide Run menu by altering registry on clients but i can’t do this on each client as i have more than 50 clients in my network. Can any1 help me?