So you want to tell Vista to require Ctrl-Alt-Del before you can logon. Just like you had in previous versions of Windows. And it's easy to do, you just have to find the proper dialog box, like the one below. You tick the checkbox, and everything is done.
Now, this dialog box should be easier to find, and I'll happily be told how to get to it normally…
But if you search Windows Help for "ctrl-alt-del", you'll get a link to a page which takes you to a dialog box that lets you set this option. In the dialog, it's on the Advanced Tab, at the bottom. If you can't find it in the help, you can just run NetplWiz.exe – that will open it for you too.
I honestly can't find any other way of opening this dialog box. But this dialog is definitely the place to set the option. I've asked Rocky Heckman (of Microsoft) how to get to this really-useful-dialog, and hopefully he'll have something for me in the next day or so. Any of you readers know how to do it?
Oh, and the reason why you might want this enabled is that you should make sure that you don't have something asking for your Windows password unless that thing is Windows. The Ctrl-Alt-Del combo will always force Windows to jump out of whatever it's running, so that you won't ever give your password away.