If you mean Safe Mode, F8 should do it.
From the online manual....
Turn on the computer. When the Dell logo appears, press <F8> several times
to access the Vista Advanced Boot Options Window.
"Top" <topretired@xxxxxx> wrote in message
> I have a Dell XPS M1530 with Vista Home Premimum. I have found no way to
> bring it up in administrator mode. I've tried F8 F11 and no joy. Any
> (I posted this before but if there was an an answer I haven't found the
> answer, search didn't help)